Cement augmentation of lag screws: an investigation on biomechanical advantages

Background

In trauma surgery, lag screws are commonly used. However, in osteoporotic bone, anchorage can be considerably compromised. This study investigates the biomechanical potential of cement augmentation in terms of improved fixation.

Methods

36 Surrogate osteoporotic bone specimens were utilised in three biomechanical experiments, each comparing 6 augmented with 6 non-augmented samples. Standard partially-threaded lag screws (Synthes) were placed following surgical standard. For the augmented groups, 0.4 ml of polymethylmethacrylate was injected into the pre-drilled hole prior to screw placement. Interfragmentary compression was determined using a cannulated ring compression sensor. Maximum torque was recorded with a torque wrench. Compressive relaxation after 24 h, relaxation after loosening and re-tightening the screw as well as maximum compression and torque at failure were measured.

Findings

Mean relaxation was significantly lower for the augmented group (p < 0.01). After 24 h, a remaining fragmental compression of 62 % for the augmented and 52 % for the non-augmented specimens was found. Loosening and re-tightening of the screw did not affect the compressive relaxation when augmentation was applied (p = 0.529), compared to an increased relaxation after re-tightening in the non-augmented group (p = 0.04). The mean maximum compression and torque until failure were significantly higher for the augmented group (p < 0.001).

Interpretation

Cement augmentation of lag screws can improve fixation stability in terms of installing and maintaining interfragmentary compression. Effects of relaxation can be reduced and re-tightening of screws is possible without compromising the fixation. Particularly in reduced bone mass, augmentation of lag screws can markedly increase the security of the technique.     

Infra-isthmal fracture is a risk factor for nonunion after femoral nailing: a case–control study

Background

The rates of nonunion after femoral nailing are currently reported to be 4.1–12.5 %. The purpose of this study was to identify the risk factors of noninfected nonunion after femoral nailing, focusing in particular on the effects of the length of the distal main fragment.

Methods

A case–control study was conducted with 105 patients, with a case (nonunion group)–control (control group) ratio of 1:2. The nonunion group (n = 35) comprised patients with consecutive symptomatic nonunions after femoral nailing who were treated in our institute; the control group (n = 70) were matched by age to the nonunion group. Type of fracture, soft tissue injury, length of femur and nail length, incidence of screw breakage, nail diameter, mean length of distal main fragment, and any episode of dynamization were retrospectively examined. Univariate and multivariate analyses were performed to elucidate the risk factors of nonunion after femoral nailing.

Results

Increased risk of nonunion after femoral nailing was associated with (1) open fracture, (2) screw breakage, (3) shorter length of a distal fragment, and (4) any episodes of dynamization. Receiver operating characteristic analysis showed that a distal fragment length of <43 % of the total femur length was the cutoff level for nonunion after nailing. The odds ratio for nonunion was 6.40 (95 % CI 2.70–15.2) when the length of the distal main fragment was <43 % of the femur length. Multivariate logistic analysis revealed that the risk of nonunion after femoral nailing increased (1) with breakage of locking screws (p = 0.0021), (2) with dynamization (p = 0.0029), (3) with a shorter distal fragment length (p = 0.0379), and (4) with an open fracture (p = 0.0397).

Conclusion

The elucidated risk factors of nonunion after femoral nailing were identified as open fracture, infra-isthmal femoral fracture, breakage of locking screw, and inappropriate dynamization. We believe that the surgeon should be consciously aware of the need for additional surgical fixation for the distal fragment when performing femoral nailing of infra-isthmal femoral fractures.     

Comparative study of the closed reduction percutaneous cannulated screw fixation and open reduction palmar locking plate fixation in the treatment of AO type A2 distal radius fractures

Introduction

The present study was designed to demonstrate the efficacy of standard 4.0 mm cannulated screw fixation by comparing it with palmar locking plate fixation in the treatment of acute, unstable, simple extra-articular distal radius fractures.

Materials and methods

We prospectively collected and retrospectively analyzed outcomes data for 65 patients aged between 18 and 60 with AO type A2 fractures treated with closed reduction, percutaneous cannulated screw fixation (CRPCS n = 34) or open reduction palmar locking plate fixation (ORPLP n = 31). Range of motion, grip strength, Gartland–Werley and QuickDASH scores were compared at 2 months after surgery, and final follow-up (mean 32 months, range 12–90). Deterioration in radiographic parameters were measured and compared. Operative time and return to preinjury activity were evaluated.

Results

Parameters did not differ significantly between the groups at either time point with respect to grip strength or range of motion, except pronation and supination; they were better in the CRPCS group (p = 0.005 and 0.025, respectively) at 2 month follow-up. The Gartland–Werley and QuickDASH scores obtained at final follow-up were similar for each group and lacked statistical significance. Group comparison for the deterioration of radiologic parameters showed no significant difference. CRPCS group had significantly shorter operative time (p = 0.001) and there was no significant differences between the groups regarding the return to preinjury activity (p = 0.129).

Conclusions

CRPCS group was found to be as successful as ORPLP group and it may be suitable in the case of young, active individuals with AO type A2 distal radius fractures.     

Laparoscopic mechanical fixation devices: does firing angle matter?

Background

A variety of permanent and absorbable tacks are available for mesh fixation during laparoscopic hernia repairs. Although manufacturers recommend deploying tacks perpendicular to the tissue, achieving this can sometimes be challenging. This study aimed to analyze comparatively the effects of angled deployment among commonly used tacks.

Methods

A piece of composite mesh was fixed to the peritoneal surface of a pig with a single tack fired at either a perpendicular (90°) or acute (30°) angle. A lap-shear test was performed to determine fixation strength. Two permanent tacks (a titanium spiral tack: Protack [PT]; and a hollow screw fastener: PermaFix [PF]) and three absorbable tackers (a solid screw: Absorbatack [AT]; a hollow screw fastener: SorbaFix [SF]; and a strap: SecurStrap [SS]) were challenged. A total of 16 samples were performed for each device at each angle. A nonabsorbable transfascial suture was used as a control condition.

Results

Transabdominal sutures had the maximum acute tensile strength (ATS) (29.9 ± 5.5 N). Protack at both 90° and 30° performed significantly better than absorbable tacks (p < 0.01). No significant difference was found among absorbable tacks at 90°. When the same construct was compared at different angles, SS and SF performance was not affected (p = 0.07 and 0.2, respectively). In contrast, PT and AT had significantly reduced fixation strength (p = 0.003 and 0.004, respectively). However, PT fired at an acute angle had fixation equal to that of absorbable tacks fired perpendicularly.

Conclusion

Transabdominal sutures performed better than tacks in the acute setting. No absorbable fixation device demonstrated superior efficacy within its class. Spiral titanium tacks provided better fixation than absorbable tacks at both perpendicular and acute angles. Moreover, titanium spiral tacks deployed at 30° performed equal to or better than absorbable tacks fired perpendicularly to the tissue. It appears that spiral titanium tacks should be strongly considered for cases in which perpendicular tack deployment cannot be achieved.     

Bioabsorbable sutures versus screw fixation of displaced tibial eminence fractures: a biomechanical study

Background

In 1995, we developed a simple and safe arthroscopic technique of anterograde stable fixation of the displaced tibial eminence fractures using a cannulated screw and washer, allowing immediate mobilisation and weight bearing. Some authors described similar end results by arthroscopic fixation of this abruption with trans-osseous sutures. We proved with the biomechanical study that the fixation with strong trans-osseous sutures provides a comparable stable fixation the same as the cannulated screw and washer. We developed a test machine for cyclic loading and a machine for measuring of the pull-out strength for this study.

Methods

A standard osteotomy of the tibial spine was performed during the cadaveric biomechanical study. We performed an arthroscopic fixation with the cannulated screw and washer in ten knees, and in another group of ten knees, arthroscopic fixation was made using two trans-osseous Orthocord? sutures. The operating time for each procedure was measured, and any possible technical complications were recorded. One thousand cycles of flexion from 0° to 90° were performed on a special loading device on all knees. The macroscopic dislocation of the fragment was measured. After the cyclic loading, all soft tissue was resected except the anterior cruciate ligament with the fixed fragment. The pull-out strength defined as translation of the tibia in anterior direction by breakage was measured with a custom-made measuring device.

Results

The average time for the screw and washer fixation was 20 min, and average time for the sutures fixation was 48 min. After cyclic loading, we did not see any dislocation of the fragment. Average pull-out strength at which fixation with a cannulated screw and washer fell was 253.42 N and mean pull-out strength at which fixation with trans-osseous sutures fell was 330.32 N. Fixation of the fragment with trans-osseous sutures was statistically significantly stronger—Wilcoxon–Mann–Whitney’s test, p = <0.00.

Conclusion

Fixation with strong trans-osseous sutures is stronger than fixation with a cannulated screw and washer on cadaveric knees. It appears that fixation with strong trans-osseous sutures allows immediate mobilisation and weight bearing like fixation with a cannulated screw and washer. Meanwhile, the time for fixation with trans-osseous sutures is significantly longer.     

Distal femoral replacement for selective periprosthetic fractures above a total knee arthroplasty

Background and aim

The management of distal femur periprosthetic fractures in the elderly remains a challenge. The aim of this study was to evaluate the results of distal segmental femur replacement as an alternative to fixation in complex distal femoral periprosthetic fractures in elderly patients.

Methods

Twelve patients were included in this prospective study, with a mean age of 78 years (range 68–90 years); incidentally, all were female. Fractures of the distal femur were classified as per Kim et al.’s classification (Clin Orthop Relat Res 446:167–175, 2006); our series included eight patients with type III and four patients with type II periprosthetic fractures. All 12 patients were treated with segmental distal femur replacement (Zimmer Inc., Warsaw, IN, USA). Nine patients required 90 cm and three patients required 130 cm of distal femur segment with a rotating hinge knee prosthesis.

Results

The mean follow up period was 20 months (range 15–28 months), with no major surgical complications reported. The mean duration of hospital stay following surgery was 12 days (range 7–36 days). All patients were mobilising full weight-bearing by day 3. All patients returned to their prior living arrangements. Ten patients returned to their original domicile, with one patient being discharged to a care home requiring minimal ambulatory assistance. The remaining two patients returned to their care homes.

Conclusions

WOMAC scores improved from the pre-injury state with a mean of 49.62 to 72.54 post-surgery (p-value of 0.0001). The Knee Society scores, possible only following surgery, had a mean value of 72. The mean VAS pain score was 1.75 (0 = no pain to 10 = worst pain ever felt). The average range of knee flexion was from 4° to 89° (range ?5° to 110°). The mean SF-36 physical functioning score was 45.64 [range 40.70–48.90; standard deviation (SD) ?2.62] and the mean SF-36 mental functioning score was 52.94 (range 45.8–57.70; SD ?3.38).     

The use of the 95-degree-angled blade plate in femoral nonunion surgery

Introduction

The 95-degree-fixed angle blade plate has been in use for decades for both acute femoral fractures and nonunions. Our objective was to examine the results of use by a single surgeon of the 95-degree-angled blade plate in proximal and distal femoral nonunion surgery.

Patients and methods

The nonunion database of a single surgeon over a 16 year period was used to identify all proximal and distal femoral nonunions that were treated with open reduction and internal fixation using the 95-degree-angled blade plate. There were 78 cases in which the blade plate was used, and 68 of 78 (87.2 % follow-up rate) were followed to a final outcome, which was defined as complete healing of the nonunion, conversion to arthroplasty, or amputation. Failure was defined as revision surgery for persistence of nonunion, conversion to arthroplasty prior to healing, or amputation. Three patients who failed were lost to follow-up prior to a final outcome.

Results

In the 71 patients who were followed to failure or complete follow-up, the rate of healing with one surgery was 77.5 % (55 of 71). Eight of 16 failures required a second surgery for persistence of nonunion and eventually went on to heal the nonunion. Eleven of the 16 failures were in patients who had a known infected nonunion. When the 21 cases of infected nonunions were excluded, the healing rate for aseptic nonunions with one surgery alone using the 95-degree-angled blade plate was 91.2 % (52 of 57) compared with 47.6?% (10 of 21) in the infected nonunion group (p?<?0.0001). Eleven patients who had healed their nonunion underwent all or partial removal of the implant for irritation or prominence.

Conclusion

The 95-degree-angled blade plate is an effective reduction aid and fixation device for aseptic nonunions of the proximal and distal femur with acceptable healing rates with one surgery alone.     

Bone mineral and stiffness loss at the distal femur and proximal tibia in acute spinal cord injury

Summary

Computed tomography and finite element modeling were used to assess bone mineral and stiffness loss at the knee following acute spinal cord injury (SCI). Marked bone mineral loss was observed from a combination of trabecular and endocortical resorption. Reductions in stiffness were 2-fold greater than reductions in integral bone mineral.

Introduction

SCI is associated with a rapid loss of bone mineral and an increased rate of fragility fracture. The large majority of these fractures occur around regions of the knee. Our purpose was to quantify changes to bone mineral, geometry, strength indices, and stiffness at the distal femur and proximal tibia in acute SCI.

Methods

Quantitative computed tomography (QCT) and patient-specific finite element analysis were performed on 13 subjects with acute SCI at serial time points separated by a mean of 3.5 months (range 2.6–4.8 months). Changes in bone mineral content (BMC) and volumetric bone mineral density (vBMD) were quantified for integral, trabecular, and cortical bone at epiphyseal, metaphyseal, and diaphyseal regions of the distal femur and proximal tibia. Changes in bone volumes, cross-sectional areas, strength indices and stiffness were also determined.

Results

Bone mineral loss was similar in magnitude at the distal femur and proximal tibia. Reductions were most pronounced at epiphyseal regions, ranging from 3.0 % to 3.6 % per month for integral BMC (p?<?0.001) and from 2.8 % to 3.4 % per month (p?<?0.001) for integral vBMC. Trabecular BMC decreased by 3.1–4.4 %/month (p?<?0.001) and trabecular vBMD by 2.7–4.7 %/month (p?<?0.001). A 3.8–5.4 %/month reduction was observed for cortical BMC (p?<?0.001); the reduction in cortical vBMD was noticeably lower (0.6–0.8 %/month; p?≤?0.01). The cortical bone loss occurred primarily through endosteal resorption, and reductions in strength indices and stiffness were some 2-fold greater than reductions in integral bone mineral.

Conclusions

These findings highlight the need for therapeutic interventions targeting both trabecular and endocortical bone mineral preservation in acute SCI.     

Distal radius fracture fixation with volar locking plates and additional bone augmentation in osteoporotic bone: a biomechanical study in a cadaveric model

Background

Fractures of the distal radius represent the most common fractures in adults. Volar locked plating has become a popular method for treating these fractures, but has been subject to several shortcomings in osteoporotic bone, such as loss of reduction and screw purchase. In order to overcome these shortcomings, cement augmentation has been proposed.

Methods

AO-type 23-A3.3 fractures were made in 8 pairs of fresh frozen osteoporotic cadaveric radial bones. All specimens were treated with volar plating, and divided into cement augmentation or non-augmentation groups (n = 8/group). Constructs were tested dynamically and load to failure, construct-stiffness, fracture gap movement and screw cutting distance were measured.

Results

Cement augmentation resulted in a significant increase in cycles and load to failure, as well as construct stiffness at loads higher than 325 N. When compared to the non-augmented group, fracture gap movement decreased significantly at this load and higher, as did screw cutting distance at the holes of the ulnar column. The cycles to failure depend on the BMD in the distal region of the radius.

Conclusion

Cement augmentation improves biomechanical properties in volar plating of the distal radius.     

Biomechanical comparison of sagittal-parallel versus non-parallel pedicle screw placement

Background

While convergent placement of pedicle screws in the axial plane is known to be more advantageous biomechanically, surgeons intuitively aim toward a parallel placement of screws in the sagittal plane. It is however not clear whether parallel placement of screws in the sagittal plane is biomechanically superior to a non-parallel construct. The hypothesis of this study is that sagittal non-parallel pedicle screws do not have an inferior initial pull-out strength compared to parallel placed screws.

Methods

The established lumbar calf spine model was used for determination of pull-out strength in parallel and non-parallel intersegmental pedicle screw constructs. Each of six lumbar calf spines (L1-L6) was divided into three levels: L1/L2, L3/L4 and L5/L6. Each segment was randomly instrumented with pedicle screws (6/45 mm) with either the standard technique of sagittal parallel or non-parallel screw placement, respectively, under fluoroscopic control. CT was used to verify the intrapedicular positioning of all screws. The maximum pull-out forces and type of failure were registered and compared between the groups.

Results

The pull-out forces were 5,394 N (range 4,221 N to 8,342 N) for the sagittal non-parallel screws and 5,263 N (range 3,589 N to 7,554 N) for the sagittal-parallel screws (p?=?0.838). Interlevel comparisons also showed no statistically significant differences between the groups with no relevant difference in failure mode.

Conclusion

Non-parallel pedicle screws in the sagittal plane have at least equal initial fixation strength compared to parallel pedicle screws in the setting of the here performed cadaveric calf spine experiments.     

Influence of the screw augmentation technique and a diameter increase on pedicle screw fixation in the osteoporotic spine: pullout versus fatigue testing

Purpose

For posterior spinal stabilization, loosening of pedicle screws at the bone-screw interface is a clinical complication, especially in the osteoporotic population. Axial pullout testing is the standard pre-clinical testing method for new screw designs although it has questioned clinical relevance. The aim of this study was to determine the fixation strength of three current osteoporotic fixation techniques and to investigate whether or not pullout testing results can directly relate to those of the more physiologic fatigue testing.

Methods

Thirty-nine osteoporotic, human lumbar vertebrae were instrumented with pedicle screws according to four treatment groups: (1) screw only (control), (2) prefilled augmentation, (3) screw injected augmentation, and (4) unaugmented screws with an increased diameter. Toggle testing was first performed on one pedicle, using a cranial-caudal sinusoidal, cyclic (1.0 Hz) fatigue loading applied at the screw head. The initial compressive forces ranged from 25 to 75 N. Peak force increased stepwise by 25 N every 250 cycles until a 5.4-mm screw head displacement. The contralateral screw then underwent pure axial pullout (5 mm/min).

Results

When compared to the control group, screw injected augmentation increased fatigue force (27 %, p = 0.045) while prefilled augmentation reduced fatigue force (?7 %, p = 0.73). Both augmentation techniques increased pullout force compared to the control (ps < 0.04). Increasing the screw diameter by 1 mm increased pullout force (24 %, p = 0.19), fatigue force (5 %, p = 0.73), and induced the least stiffness loss (?29 %) from control.

Conclusions

For the osteoporotic spine, screw injected augmentation showed the best biomechanical stability. Although pullout testing was more sensitive, the differences observed were not reflected in the more physiological fatigue testing, thus casting further doubt on the clinical relevance of pullout testing.     

Impaired trabecular and cortical microarchitecture in daughters of women with osteoporotic fracture: the MODAM study

Summary

We investigated the familial resemblance of bone microarchitecture parameters between postmenopausal mothers with fragility fracture and their premenopausal daughters using high-resolution peripheral quantitative computed tomography (HR-pQCT). We found that daughters of women with fracture have lower total volumetric bone mineral density (vBMD), thinner cortices, and impaired trabecular microarchitecture at the distal radius and tibia, compared to controls.

Introduction

Familial resemblance of areal bone mineral density (aBMD) in mothers and daughters has been widely studied, but not its morphological basis, including microarchitecture.

Methods

We compared aBMD, vBMD, bone size, and bone microarchitecture at the distal radius and tibia assessed by HR-pQCT in mothers and their premenopausal daughters. We included 115 women aged 43?±?8 years whose mothers had sustained a fragility fracture and 206 women aged 39?±?9 years whose mothers had never sustained a fragility fracture.

Results

Women whose mothers had fracture had significantly (p?<?0.05) lower aBMD at the lumbar spine, total hip, femoral neck, mid-distal radius, and ultradistal radius compared to controls. In similar multivariable models, women whose mothers had a fracture had lower total vBMD at the distal radius (?5 %, 0.3 standard deviation [SD]; p?<?0.005) and distal tibia (?7 %, 0.4 SD; p?<?0.005). They also had lower cortical thickness and area at the distal radius (?5 %, 0.3 SD and ?4 %, 0.2 SD, respectively; p?<?0.005) and at the distal tibia (?6 %, 0.3 SD and ?4 %, 0.3SD, respectively; p?<?0.005). Trabecular vBMD was lower at the distal radius (?5 %, 0.3 SD; p?<?0.05) and tibia (?8 %, 0.4 SD; p?<?0.005), with a more spaced and heterogeneous trabecular network (4 and 7 % at the radius and 5 and 9 %, at the tibia, p?<?0.05, for Tb.Sp and Tb.Sp.SD, respectively).

Conclusion

Premenopausal daughters of women who had sustained fragility fracture have lower total and trabecular vBMD, thinner cortices, as well as impaired trabecular microarchitecture at the distal radius and tibia, compared with premenopausal daughters of women without fracture.     

The effect of two different trochanteric nail lag-screw designs on fixation stability of four-part intertrochanteric fractures: a clinical and biomechanical study

Objectives

To compare lag-screw sliding characteristics and fixation stability of two cephalomedullary nails (CMN) with different lag-screw designs (solid and telescopic), we conducted a biomechanical study and an analysis of clinical results.

Methods

Six pairs of cadaver femurs with simulated intertrochanteric fractures were randomly assigned to one of two CMN fixations. Femur constructs were statically then cyclically loaded on an MTS machine. Lag-screw sliding and inferior and lateral femoral head displacements were measured, following which failure strength of the construct was determined. Forty-five patients with intertrochanteric fractures treated with these CMN were identified. Medical records and radiographs were reviewed and analyzed using Fisher’s exact test and Student’s t test to determine lag-screw sliding.

Results

No difference was seen with cycling in inferior femoral head displacement between the two screw designs. The solid screw had an average inferior head displacement of 1.75 mm compared with 1.59 mm for the telescoping screw (p = 0.772). The solid lag screws slid an average of 2.79 mm lateral from the nail, whereas the telescoping screws slid an average of 0.27 mm (p = 0.003). In our clinical review, the average lateral sliding of the telescoping screw was 0.5 mm and of the solid screw was 3.7 mm (p < 0.001). Despite differences in lateral sliding, there were no reoperations for prominent or painful hardware in either group.

Conclusions

Both designs are acceptable devices for stabilization of intertrochanteric fractures. Clinical and biomechanical data demonstrate greater lateral sliding in the solid lag-screw group, making for greater potential for lateral-sided hip pain in CMNs with solid lag screws as opposed to telescoping lag screws.     

Biomechanical effect of bone cement augmentation on rotational stability and pull-out strength of the Proximal Femur Nail Antirotation™

Introduction

After surgical treatment of osteoporotic hip fractures, complications such as implant cut-out are reported to be high and implant failure often is associated with poor bone quality. As augmentation is reported to enhance implant anchorage, the aim of our study was to investigate the effect of bone cement augmentation on the rotational stability and the pull-out resistance of the Proximal Femur Nail Antirotation™ (PFNa) blade.

Materials and methods

A total of 18 fresh-frozen femoral heads (mean age 68 years, standard deviation (SD) 8.2) were scanned with quantitative computed tomography (qCT) for bone mineral density (BMD) measurements and instrumented with a PFNa blade. Nine specimens were augmented with a mean volume of 4.4 ml Traumacem V+. After cement consolidation, the blade was rotated for 60° for the rotational test. Subsequently, the blade was extracted from the specimens. Force, torque, displacement and angle were recorded constantly.

Results

In the rotational test, the mean maximum torque in the augmented group (17.2 Nm, SD 5.0) was significantly higher (p = 0.017) than in the non-augmented group (11.7 Nm, SD 3.5). The pull-out test also yielded a significant difference (p = 0.047) between the augmented (maximum pullout force: 2315.2 N, SD 1060.6) and the non-augmented group (1180.4 N, SD 1171.4).

Discussion

Augmentation of femoral heads yielded a significantly superior rotational stability, as well as an enhanced pull-out resistance, compared to the non-augmented state. However, the higher the BMD of the specimens, the lower was the effect of augmentation on the rotational stability. Therefore, augmentation can be a good clinical tool to enhance implant anchorage in osteoporotic bone.     

ACL reconstruction using bone–patella tendon–bone autograft: press-fit technique vs. interference screw fixation

Purpose

The gold standard in ACL reconstructions has been the bone–patellar tendon–bone autograft fixed with interference screws. This prospective, randomized clinical trial aimed to compare two methods of fixation for BPTB grafts: press-fit fixation vs. interference screw, over a 12-month follow-up interval.

Methods

158 patients with an average age of 29.8 years, between 2011 and 2012, were treated for torn ACL. 82 patients underwent reconstruction with BPTB autograft with a press fit fixation technique, and in 76 cases an interference screw was used. At the time of final follow-up, 71 patients in press-fit group and 65 patients in interference screw group were evaluated in terms of return to pre-injury activity level, pain, knee stability, range of motion, IKDC score and complications.

Results

At 12-month follow-up, 59 (83 %) and 55 (85 %) in press-fit and screw group, respectively had good-to-excellent IKDC score (p > 0.05). The mean laxity assessed using a KT-1000 arthrometer improved to 2.7 and 2.5 mm in press-fit and screw group, respectively. Regarding Lachman and pivot shift test, there was a statistically significant improvement in the integrity of the ACL in both the groups, but no significant differences was noted between groups. There were no significant differences in terms of femur circumference difference, effusion, knee range of motion, pain and complications.

Conclusions

The press-fit technique is an efficient procedure. Its outcome was comparable with the interference screw group. Furthermore it has unlimited bone-to-bone healing, no need for removal of hardware, ease for revision and cost effectiveness.     

Position of polyaxial versus monoaxial screws in locked plating for proximal humeral fractures: analysis of a prospective randomized study

Background

Aim of the study was to compare the chosen position of polyaxial locking screws with the position of monoaxial screws in the humeral head of proximal humeral fractures treated by locked plating.

Methods

In a prospective randomized observational study, 124 consecutive patients (mean age 70.9 ± 14.8 years) sustaining a displaced proximal humeral fracture were treated with either monoaxial or polyaxial screw-inserted locking plate fixation. The chosen positions of locking screws were identified from standardized postoperative radiographs in anteroposterior and outlet-view, with regard to a regional mapping of the humeral head.

Results

In monoaxial locking technique, a mean of 6 screws purchased the humeral head (95 % CI 5.1–6.2), and in polyaxial locking technique, a mean of 4 screws (95 % CI 3.3–4.5), respectively. Screws were placed in the regions superolateral: monoaxial 24.8 %, polyaxial 20.7 % (p = 0.49); superomedial: monoaxial 21.9 %, polyaxial 20.0 % (p = 0.433); inferolateral: monoaxial 32.5 %, polyaxial 35.0 % (p = 0.354); inferomedial: monoaxial 20.8 %, polyaxial 24.2 % (p = 0.07), superoposterior: monoaxial 45.5 %, polyaxial 30.8 % (p = 0.57); superoanterior: monoaxial 4.4 %, polyaxial 8.3 % (p = 0.33); inferoposterior: monoaxial 22.5 %, polyaxial 29.8 % (p = 0.49) and inferoanterior: monoaxial 27.5 %, polyaxial: 31.2 % (p = 0.09).

Conclusion

The chosen screws’ position in monoaxial and polyaxial locking plate fixation of displaced proximal humeral fractures do not differ significantly. However, loss of fixation is observed more frequently if the fixation did not include at least one screw within the superoposterior region of the humeral head, suggesting that a screw purchasing the superoposterior region is beneficial in locked plating of proximal humeral fractures.

Level of evidence

Treatment Study, Level II.     

Micro-finite element analysis applied to high-resolution MRI reveals improved bone mechanical competence in the distal femur of female pre-professional dancers

Summary

Micro-finite element analysis applied to high-resolution (0.234-mm length scale) MRI reveals greater whole and cancellous bone stiffness, but not greater cortical bone stiffness, in the distal femur of female dancers compared to controls. Greater whole bone stiffness appears to be mediated by cancellous, rather than cortical bone adaptation.

Introduction

The purpose of this study was to compare bone mechanical competence (stiffness) in the distal femur of female dancers compared to healthy, relatively inactive female controls.

Methods

This study had institutional review board approval. We recruited nine female modern dancers (25.7?±?5.8 years, 1.63?±?0.06 m, 57.1?±?4.6 kg) and ten relatively inactive, healthy female controls matched for age, height, and weight (32.1?±?4.8 years, 1.6?±?0.04 m, 55.8?±?5.9 kg). We scanned the distal femur using a 7-T MRI scanner and a three-dimensional fast low-angle shot sequence (TR/TE?=?31 ms/5.1 ms, 0.234 mm?×?0.234 mm?×?1 mm, 80 slices). We applied micro-finite element analysis to 10-mm-thick volumes of interest at the distal femoral diaphysis, metaphysis, and epiphysis to compute stiffness and cross-sectional area of whole, cortical, and cancellous bone, as well as cortical thickness. We applied two-tailed t-tests and ANCOVA to compare groups.

Results

Dancers demonstrated greater whole and cancellous bone stiffness and cross-sectional area at all locations (p?<?0.05). Cortical bone stiffness, cross-sectional area, and thickness did not differ between groups (>0.08). At all locations, the percent of intact whole bone stiffness for cortical bone alone was lower in dancers (p?<?0.05). Adjustment for cancellous bone cross-sectional area eliminated significant differences in whole bone stiffness between groups (p?>?0.07), but adjustment for cortical bone cross-sectional area did not (p?<?0.03).

Conclusions

Modern dancers have greater whole and cancellous bone stiffness in the distal femur compared to controls. Elevated whole bone stiffness in dancers may be mediated via cancellous, rather than cortical bone adaptation.     

Ergebnisse bei der Versorgung per- und subtrochantärer Femurfrakturen

Background

Can the helical blade in proximal femur nailing antirotation (PFNA) reach a better bony fixation than proximal femur nailing (PFN), thereby decreasing complication rates and improving clinical outcomes especially in osteoporotic bone?

Materials and methods

In a retrospective study complications and clinical treatment results of pertrochanteric and subtrochanteric femoral fractures were analyzed. For this purpose a group of patients stabilized with PFN (n=65) were compared to a patient group treated with PFNA (n=66). Objective and subjective parameters were acquired and analyzed by clinical follow-up studies using the Merle d’Aubigné score and X-ray evaluation. Individual bone quality was analyzed radiologically by determining the Singh index. The mean follow-up time was 7 months in each group.

Results

The PFNA showed a decrease in postoperative implant-associated complications especially in osteoporotic bone and unstable fracture types.

Conclusion

The philosophy of the PFNA blade with better fixation through an increased implant-bone-interface and smaller cross-section, compaction of cancellous bone as well as an antirotational fixation, seems to show advantages compared to the double screw system of the PFN.     

Bone mineral loss at the proximal femur in acute spinal cord injury

Summary

This study used quantitative computed tomography to assess changes in bone mineral at the proximal femur after acute spinal cord injury (SCI). Individuals with acute SCI experienced a marked loss of bone mineral from a combination of trabecular and endocortical resorption. Targeted therapeutic interventions are thus warranted in this population.

Introduction

SCI is associated with a rapid loss of bone mineral and an increased rate of fragility fracture. Some 10 to 20 % of these fractures occur at the proximal femur. The purpose of this study was to quantify changes to bone mineral, geometry, and measures of strength at the proximal femur in acute SCI.

Methods

Quantitative computed tomography analysis was performed on 13 subjects with acute SCI at serial time points separated by a mean of 3.5 months (range, 2.6–4.8 months). Changes in bone mineral content (BMC) and volumetric bone mineral density (vBMD) were quantified for integral, trabecular, and cortical bone at the femoral neck, trochanteric, and total proximal femur regions. Changes in bone volumes, cross-sectional areas, and surrogate measures of compressive and bending strength were also determined.

Results

During the acute period of SCI, subjects experienced a 2.7–3.3 %/month reduction in integral BMC (p?<?0.001) and a 2.5–3.1 %/month reduction in integral vBMD (p?<?0.001). Trabecular BMC decreased by 3.1–4.7 %/month (p?<?0.001) and trabecular vBMD by 2.8–4.4 %/month (p?<?0.001). A 3.9–4.0 %/month reduction was observed for cortical BMC (p?<?0.001), while the reduction in cortical vBMD was noticeably lower (0.8–1.0 %/month; p?≤?0.01). Changes in bone volume and cross-sectional area suggested that cortical bone loss occurred primarily through endosteal resorption. Declines in bone mineral were associated with a 4.9–5.9 %/month reduction in surrogate measures of strength.

Conclusions

These data highlight the need for therapeutic interventions in this population that target both trabecular and endocortical bone mineral preservation.     

Nailing versus plating for comminuted fractures of the distal femur: a comparative biomechanical in vitro study of three implants

Purpose

The purpose of our study was to determine the biomechanical properties of three different implants utilized for internal fixation of a supracondylar femur fracture. The retrograde supracondylar nail (SCN), the less invasive stabilization system plate (LISS) and the distal femoral nail (DFN) were tested and their biomechanical properties compared.

Methods

Twenty pairs of fresh-frozen human femura were used. Each femur was osteotomised to simulate a comminuted supracondylar fracture (AO/OTA 33.A3) and then randomized to fracture fixation with either SCN (n=9) or LISS (n=9). Each contralateral femur was stabilized with DFN as a control (n=18). Two femur pairs were spent on pretesting. All femura were subjected to axial (10–500 N) and torsional (0.1–14 Nm) loading.

Results

Eighteen matched femur pairs were analyzed. The post-loading median residual values were 49.78, 41.25 and 33.51% of the axial stiffness of the intact femur and 59.04, 62.37 and 46.72% of the torsional stiffness of the intact femur in the SCN, LISS and DFN groups. There were no significant differences between the three implants concerning axial and torsional stiffness.

Conclusions

All implants had sufficient biomechanical stability under physiological torsional and axial loading. All three implants have different mechanisms for distal locking. The SCN nail with the four-screw distal interlocking had the best combined axial and torsional stiffness whereas the LISS plate had the highest torsional stiffness.