Adjacent segment hypermobility after lumbar spine fusion: No association with progressive degeneration of the segment 5 years after surgery

Background and purpose?Increased intradiscal pressure and relative segmental hypermobility are in vitro observations supporting the idea of increased postoperative load being a reason for progressive degeneration of the free mobile segment adjacent to a lumbar fusion. These mechanisms have been difficult to confirm in clinical studies, and an alternative theory claims instead that the adjacent segment degeneration follows a natural degenerative course in patients who are predisposed. We examined 9 patients 5 years after lumbar fusion, to assess whether relative hypermobility of the segment adjacent to fusion could be correlated to progressive degeneration of the same segment.

Patients and methods?The 9 patients, all of whom had been treated with a lumbar fusion after a preoperative intervertebral mobility assessment by spinal RSA, were re-examined 5 years after surgery. The intervertebral translations of the vertebra proximal to the fusion were determined by RSA and compared to the mobility of the same lumbar segment before fusion. The disc height and any progressive reduction at the two levels proximal to the one fused were measured on conventional radiographs.

Results?Adjacent segment mobility 5 years after fusion—expressed as mean transverse, vertical, and sagittal translation of the vertebra proximal to fusion— was not significantly changed compared to the mobility measured before surgery. Increased mobility of the segment seen in 5 individual patients was not associated with progressive degeneration of the same segment or to a poor clinical outcome.

Interpretation?Hypermobility of the segment adjacent to fusion is not a general finding. Increased mobility that can be seen in certain individuals does not impair the 5-year result. The significance of mechanical alterations in adjacent segment degeneration is uncertain, and it is possibly overestimated.     

Stable fixation of the ulnar component in the Kudo elbow prosthesis. A radiostereometric (RSA) study of 13 prostheses with 2-year follow-up

Background Concern has been expressed about the large number of radiolucent lines around the ulnar component of the Kudo elbow prosthesis in medium-term follow-up.

Patients and methods We studied the metal-backed cemented ulnar component in 13 Kudo elbow prostheses (type 5) using radiostereometric analysis (RSA). All patients had rheumatoid arthritis. There were 2 men and 9 women with a mean age of 55 years. 2 were operated bilaterally. The metal-backed ulnar component was marked with three 0.8 mm tantalum spheres and the proximal ulna with 5 spheres of 0.8 or 1.0 mm diameter. The initial RSA examination was performed during the first week after the operation. Further examinations were done at 4, 12 and 24 months. Conventional radiographs were taken during the first week postoperatively, and at 12 and 24 months.

Results Translations (medial/lateral, antero/poste-rior and proximal/distal) were less than 0.5 mm in all but 1 patient who had a maximal translation of 3.4 mm distally. The mean rotations around all three axes were less than 0.4 degrees. The patient who had a translation of 3.4 mm also had varus angulation exceeding 4 degrees. This patient also had progressive circumferential radiolucent lines on conventional radiographs. The Mayo elbow score increased from 40 (25-65) before surgery to 92 (45-100) at 2 years.

Interpretation The fixation of the metal-backed ulnar component of the Kudo elbow prosthesis at 2 years is good.     

High-precision measurements of cementless acetabular components using model-based RSA: an experimental study

Background In RSA, tantalum markers attached to metal-backed acetabular cups are often difficult to detect on stereo radiographs due to the high density of the metal shell. This results in occlusion of the prosthesis markers and may lead to inconclusive migration results. Within the last few years, new software systems have been developed to solve this problem. We compared the precision of 3 RSA systems in migration analysis of the acetabular component.

Material and methods A hemispherical and a nonhemispherical acetabular component were mounted in a phantom. Both acetabular components underwent migration analyses with 3 different RSA systems: conventional RSA using tantalum markers, an RSA system using a hemispherical cup algorithm, and a novel modelbased RSA system.

Results We found narrow confidence intervals, indicating high precision of the conventional marker system and model-based RSA with regard to migration and rotation. The confidence intervals of conventional RSA and model-based RSA were narrower than those of the hemispherical cup algorithm-based system regarding cup migration and rotation.

Interpretation The model-based RSA software combines the precision of the conventional RSA software with the convenience of the hemispherical cup algo-rithm-based system. Based on our findings, we believe that these new tools offer an improvement in the measurement of acetabular component migration.     

Adjacent segment degeneration after lumbar spinal posterolateral fusion with instrumentation in elderly patients

This retrospective study investigated adjacent segments radiologically and clinically after posterolateral fusion of the lumbar spine with instrumentation. Thirty-two patients over 60 years old with a postoperative follow-up of at least 4 years were included. These patients all met the criteria of a postoperative symptom-free period of over 2 years, evident fusion mass seen on plain radiographs, and no implant breakage or loosening. There was 81.3% excellent and good clinical results (26/32). For all patients, flexion and extension views of the lumbar spine were done preoperatively and postoperatively. Adjacent segments below the fusion, above the fusion, and cranial to the above adjacent segment were examined. Three patients each with translation > 4 mm in adjacent segments were found in both the short and long (> or = 3 segments) fusion groups. The incidence was 16.7% (3/18) in the short fusion group and 21.4% (3/14) in the long fusion group. However, no statistically significant difference (p = 0.7878) was found according to the Fisher exact test. Comparing the effect of different types of instruments, there still was no statistically significant difference (p = 0.1161) between the VSP plate and Isola rod groups in inducing degeneration of adjacent segments after posterolateral fusion of the lumbar spine. After measuring the mobility of degenerated adjacent segments, relative hypermobility was more likely responsible for the accelerated degeneration rather than the absolute increase of mobility.     

Women with low-energy fracture should be investigated for osteoporosis

Introduction Treatment of osteoporosis is becoming more effective, but methods to identify patients who are most suitable for investigation and treatment are still being debated. Should any type of fracture have higher priority for investigation of osteoporosis than any other? Is the number of previous fractures useful information?

Material and methods We investigated 303 consecutive women patients between 55 and 75 years of age who had a newly diagnosed low-energy fracture. They answered a questionnaire on previous fractures which also dealt with risk factors. Bone mineral density (BMD) was measured at the hip, lumbar spine, and forearm.

Results The distribution of fracture location was: distal forearm 56%, proximal humerus 12%, vertebra 18%, and hip 13%, all with similar age. Half of the subjects had had at least one previous fracture before the index fracture, 19% had had two previous fractures, and 6% had had three or more previous fractures. Patients with vertebral or hip fracture had lower BMD and had had more previous fractures than patients with forearm or humerus fractures. There was an inverse correlation between number of fractures and BMD. Osteoporosis was present in one-third of patients with forearm fracture, in one-half of those with hip or humerus fracture, and in two-thirds of those with vertebral fracture.

Interpretation Vertebral fractures were the strongest marker of low BMD and forearm fractures the weakest. The number of previous fractures is helpful information for finding the most osteoporotic patient in terms of severity. Investigation of osteoporosis therefore seems warranted in every woman between the ages of 55 and 75 with a recent low-energy fracture, with highest priority being given to those with vertebral, hip, or multiple fractures.     

The Polarus intramedullary nail for proximal humeral fractures: outcome in 28 patients followed for 1 year

Background One of the new treatment options for proximal humeral fractures is the minimally invasive intramedullary nail. In this study, we reviewed the early clinical results after 1 year.

Patients and methods 35 patients with proximal humeral fractures were treated using the Polarus nail. In 14 cases the initial treatment was operative; the other 21 patients were initially treated nonoperatively. 19 patients had a 2-part fracture, 5 had a 3-part fracture and 2 had a 4-part fracture. In 9 patients the fracture extended metaphyseally. The functional outcome was assessed by the Constant score.

Results 28 patients were available for 1-year followup. 17 patients showed excellent functional outcome (with an average Constant score of 81%). 6 patients required revision surgery, 1 because of nonunion and 1 because of an avascular necrosis. 4 others were reoperated because of inadequate position of the osteosynthesis or migration of the screws.

Interpretation The Polarus nail is of value for (displaced) 2-, 3-, and even 4-part proximal humeral fractures and enables early postoperative mobilization with a limited amount of pain.     

Survivorship of the KUDO total elbow prosthesis--comparative study of cemented and uncemented ulnar components: 89 cases followed for an average of 6 years

Background The Kudo total elbow prosthesis (TEP) is a well-established implant with good mid-term results. The ulnar component can be placed with or without cement, and the humeral component is normally placed without cement.

Methods 89 Kudo type-5 total elbow prostheses were evaluated after a mean follow-up of 6 (1.7-11) years. The indication for joint replacement was rheumatoid arthritis in all cases. 49 prostheses were placed without cement. In 40 cases, the ulnar component was cemented and the humeral component was uncemented.

Results In the uncemented group, 7 revisions had taken place. 3 of these ulnar components were shortstemmed and 4 were long-stemmed. No revisions had been performed in the hybrid group. In the uncemented group another 7 patients showed progressive radiolucencies, while 3 patients in the hybrid group showed progressive radiolucencies.

Interpretation In this group of RA patients, the survivorship of the cemented ulnar component was better than that of the uncemented ulnar component.     

Systemic zoledronate precoating of a bone graft reduces bone resorption during remodeling

Background Cartilage degeneration often occurs after osteosynthesis of a devascularized intermediary fragment in a joint fracture, in mosaicplasty or in whole-joint toe-to-finger transplantation. Hypothetically, the degeneration is secondary to a collapse of the transferred subchondral bone as it remodels during high mechanical load. Bisphosphonates are used to reduce resorption of necrotic bone. We tested a systemic pretreatment before harvesting the graft in order to protect the bone and cartilage against collapse and secondary arthrosis.

Methods Rats were given one zoledronate injection and bone grafts were harvested. The grafts were frozen, thawed and placed into bone chambers, and implanted into another batch of rats. Graft resorption and new bone formation was measured by histomorphometric analysis and compared with untreated grafts.

Results In the remodeled area of the controls, the graft was almost totally resorbed and replaced by bone marrow. In the zoledronate-treated specimens, the graft remained and the graft trabeculas were lined with new bone. By histomorphometry, the total amount of bone (graft plus new bone) within the remodeled area was 16% in the zoledronate-treated grafts and 5% in the controls (p = 0.003).

Interpretation A bone graft can be pretreated with bisphosphonate and remain protected against resorption once implanted again. ▪     

Is there increased intervertebral mobility in isthmic adult spondylolisthesis? A matched comparative study using roentgen stereophotogrammetry

STUDY DESIGN: By roentgen stereophotogrammetric technique, the intervertebral mobility of the spondylolytic segment in eight patients was measured and compared with the mobility of eight nonspondylolytic patients matched according to sex, afflicted segment, and grade of disc degeneration. OBJECTIVES: To compare the intervertebral mobility of a spondylolytic segment with the mobility of a segment without spondylolysis in adult patients with back pain. SUMMARY OF BACKGROUND DATA: Evidenced by the resulting olisthetic deformity and supported by the outcome from prior investigations, spondylolysis is assumed to induce spinal segmental instability/hypermobility. METHODS: After percutaneous application of tantalum indicators for roentgen stereophotogrammetric technique, the intervertebral translations of the spondylolytic fifth lumbar vertebra were measured in eight adult patients with low back pain and low-grade olisthesis. Eight other patients without spondylolysis but with low back pain presumably on degenerative basis were chosen for comparison and had an identical measuring procedure using roentgen stereophotogrammetric technique. The two groups were matched in pairs according to sex, afflicted segment, and grade of disc degeneration. RESULTS: No significant difference was registered considering the intervertebral mobility for matched pairs in the two groups neither along the sagittal nor the vertical axis. The transverse translations were mostly negligible in both groups. CONCLUSION: The spondylolytic defect in pars interarticularis does not cause permanent instability/hypermobility detectable in the adult patient with low back pain and low-grade olisthesis.     

Knee arthrodesis with the Sheffield external ring fixator: fusion in 6 of 10 consecutive patients

Background Knee arthrodesis with external fixation (XF) is a possible salvage procedure for infected total knee arthroplasties (TKA). We report the outcome in 10 patients who underwent arthrodesis with the Sheffield Ring Fixator.

Patients and methods The patients had primary arthrosis in 8 cases; 2 cases were due to rheumatoid arthritis and sclerodermia. The mean time between the primary TKA and arthrodesis was 6 (0.5-14) years. The average age at arthrodesis was 69 years. The average follow-up period was 10 months.

Results Stable fusion was obtained in 6 patients after a mean XF time of 3.6 (2-4) months. 1 patient was referred to another hospital because of nonunion. This patient showed fusion with intramedullary nailing after 7 months. 3 nonunion patients required permanent bracing. 7 patients had pin tract infections. Infections healed in all patients.

Interpretation The Sheffield Ring Fixator gives an acceptable fusion rate for arthrodesis in the infected TKA, with limited complications.     

脊柱融合术后相邻节段退变的病因及其影响因素

近年来,随着脊柱融合手术的急剧增加和内固定器械的广泛应用,邻近节段退变性疾病逐渐引起人们的关注,依据临床症状判定其发生率约为5.2%～18.5%,其最常见的病理变化是椎间盘退变。导致相邻节段退变的原因包括邻近节段关节突负荷增加、活动度增大和邻近间盘内压增高,而邻近节段退变的影响因素:脊柱内固定、融合节段、矢状面上的曲度、邻近节段椎间盘退变及患者自身的特点。关于邻近节段退变的治疗,若融合术后患者的症状与邻近节段退变的病理相符时,外科干预强调充分减压和扩大融合节段,但是结果并不确切。     

Tartrate-resistant acid phosphatase 5b (TRAP 5b) as a marker of osteoclast activity in the early phase after cementless total hip replacement

Background After total hip replacement, increased bone metabolism is seen. A local periprosthetic osteopenia can be measured by dual-energy X-ray absorptiometry (DXA), but it is still unkown whether biochemical markers can be used to monitor the local remodeling at an earlier stage.

Patients and methods In this prospective study we compared the biochemical markers tartrate-resistant acid phosphatase 5b (TRAP 5b), bone ALP, osteocalcin and CrossLaps with periprosthetic DXA in 17 consecutive patients after uncemented total hip replacement.

Results We found a highly significant early increase in TRAP 5b after 2 weeks and 6 weeks, which was followed by a densitometrically detectable decrease in bone mineral density after 26 weeks, especially in periprosthetic section Gruen zone 7. Bone ALP and osteocalcin levels as markers of osteoblast activity, and also Cross-Laps as a further marker of osteoclast activity, did not appear to allow any significant prediction of local bone remodeling.

Discussion Our findings show that TRAP 5b is a sensitive parameter for monitoring of osteoclast activity after cementless total hip replacement, and may predict local osteopenia.     

Primary spinal segment stability with a stand-alone cage: in vitro evaluation of a successful goat model

Background Interbody cages have been developed to restore disk height and to increase stability of the spinal segment, and thereby enhance fusion. However, they often prove inadequate as a stand-alone device. It is unknown how much primary stability is required to facilitate fusion. In various goat studies, we have obtained spinal fusion routinely with a stand-alone cage device. However, data covering the mechanical conditions under which these fusions have been obtained are lacking. In this study, we addressed the issue of primary stability.

Methods We used an established goat model for spinal fusion in vitro. 48 native lumbar spine segments were mechanically tested in flexion/extension, axial torsion (left/right), anterior/posterior shear, and left/right lateral bending. Then all segments were provided with a titanium cage using the exact surgical procedure of our earlier in vivo studies, and the mechanical tests were repeated.

Under shear force and axial torsion, a significant loss of stiffness was seen in the operated segments as compared to nonoperated controls. No increase in stiffness was found in any of the loading directions.

Interpretation Cage implantation in a lumbar spinal segment does not increase immediate postoperative stability as compared to the native segment in this goat model. This is attributable to both the annular damage during cage implantation and the subsequent loss of segment height. Yet previous in vivo studies using this goat model have generally shown fusion. This implies that high primary segment stability is not required for fusion or, alternatively, that the tested range of motion of the spinal segment in vitro does not occur at these magnitudes in vivo.     

Mechanical evaluation of a new minimally invasive device for stabilization of proximal humeral fractures in elderly patients: a cadaver study

Background Treatment of proximal humerus fractures in elderly patients is challenging because of reduced bone quality. We determined the in vitro characteristics of a new implant developed to target the remaining bone stock, and compared it with an implant in clinical use.

Methods Following osteotomy, left and right humeral pairs from cadavers were treated with either the Button-Fix or the Humerusblock fixation system. Implant stiffness was determined for three clinically relevant cases of load: axial compression, torsion, and varus bending. In addition, a cyclic varus-bending test was performed.

Results We found higher stiffness values for the humeri treated with the ButtonFix system—with almost a doubling of the compression, torsion, and bending stiffness values. Under dynamic loading, the ButtonFix system had superior stiffness and less K-wire migration compared to the Humerusblock system.

Interpretation When compared to the Humerusblock design, the ButtonFix system showed superior biomechanical properties, both static and dynamic. It offers a minimally invasive alternative for the treatment of proximal humerus fractures.     

Serum total acid phosphatase for monitoring the clinical course of giant cell tumors of bone--26 patients with 5 local recurrences

Background Giant cell tumor of bone (GCT) is a bone-destroying tumor that sometimes recurs locally after treatment. A recent study showed increased levels of serum total acid phosphatase (TACP).

Methods We assessed TACP in the serum of 26 patients with primary GCT, and in 5 of them who developed a local recurrence.

Results We found a correlation between TACP level in serum and tumor size. TACP levels that were elevated preoperatively in patients with GCT became normalized after surgery, but increased in 3 of the 5 patients with local recurrence.

Interpretation TACP could be used as a tumor marker for monitoring response to treatment of GCT.     

Prolonged thromboprophylaxis with Dalteparin during immobilization after ankle fracture surgery: a randomized placebo-controlled, double-blind study

Background Skeletal trauma and immobilization are well-known risk factors for deep vein thrombosis (DVT) and pulmonary embolism (PE). While prophylaxis against thromboembolic complications has become routine after major orthopedic surgery, whether or not prophylaxis after minor surgery and lower limb immobilization is necessary is still under debate.

Methods In a double-blind, placebo-controlled study, 272 consecutive patients were randomized to receive either thromboprophylaxis with Dalteparin (n = 136) or placebo (n = 136) for 5 weeks after ankle fracture surgery. All patients received 1 week of initial treatment with Dalteparin before randomization. A unilateral phlebography was performed when the cast was removed.

Results The overall incidence of DVT was 21% (95% CI: 13-29%) in the Dalteparin group and 28% (CI: 19- 37%) in the placebo group (risk ratio = 0.8, CI: 0.6-1.1; p = 0.3). The incidence of proximal DVTs was 4% and 3%, respectively. No major bleeding occurred.

Interpretation We found no significant difference in the incidence of DVT between the 2 treatment groups and our results do not support prolonged thromboprophylaxis. The overall incidence of DVT was high, reflecting the potential risk of PE and post-thrombotic syndrome after ankle fracture surgery. Most of the DVTs were asymptomatic, however, and were located in distal veins.     

Outcome after treatment of complications of Gamma nailing: a prospective study of 554 trochanteric fractures

Background A high reoperation rate has been the main reason why Gamma nailing should not be recommended for routine use in the treatment of trochanteric fractures. We compared the outcome after reoperation to the outcome after primary surgery with Gamma nailing.

Methods In a series of 554 patients, we compared the outcome in 52 patients who were reoperated with that in 502 patients who had no reoperations. We assessed mortality, pain, walking ability and habitat at follow-up.

Results The most common reason for reoperation was new fracture around the implant (17), local pain after healed fracture (11), nonunion (9) and cut-out (8). A second reoperation was required in 9/52 patients. The mortality was significantly lower in the reoperated cases at 30 days and at 1-5 years, but not at 120 days, and there were no significant differences in the other outcome parameters.

Interpretation Reoperation did not lead to a worse clinical outcome, nor to increased mortality.     

Talonavicular arthrodesis or triple arthrodesis: peak pressure in the adjacent joints measured in 8 cadaver specimens

Background Talonavicular arthrodesis is a differential indication for triple arthrodesis. Differences regarding intraarticular pressure loads on the adjacent joints have not been investigated to date, but they are of clinical relevance when considering long-term joint degeneration.

Methods We used a dynamic foot model to measure intraarticular peak pressures with electronic sensors in 8 anatomical specimens in different areas of the ankle joint and in the naviculocuneiform joint. Force was applied to extrinsic tendons via cables attached to computer- regulated hydraulic cylinders. A ground reaction force was simulated in a tilting angle- and force-controlled translation stage.

Results We measured significantly higher peak pressures in the ankle joint after triple arthrodesis (5.7 Mpa) than after talonavicular arthrodesis (5.2 Mpa), with differences especially in the anterior section (5.2 Mpa as compared to 4.6 Mpa). Centrally, the peak pressure was similar, at 4.6 MPa and 4.5 Mpa, respectively. In the posterior area, the peak pressure after triple arthrodesis was lower (4.1 MPa as opposed to 4.4 Mpa). After triple arthrodeses, we measured higher values laterally/medially in the ankle joint (5.5 MPa/4.6 Mpa) than after talonavicular arthrodesis (5.1 MPa/4.4 Mpa). In the naviculocuneiform joint, we again saw higher peak pressures after triple arthrodesis than after talonavicular arthrodesis.

Interpretation Our findings from this cadaver study indicate a lower and more evenly distributed peak pressure load in the ankle joint after talonavicular arthrodesis than after triple arthrodesis; thus, mechanically, a selective arthrodesis appears to be more favorable. In contrast, triple arthrodesis leads to an increase in peak pressure in the ankle joint, which may in turn lead to joint degeneration.     

Postoperative clodronate decreases prosthetic migration: 4-year follow-up of a randomized radiostereometric study of 50 total knee patients

Background We have previously reported that 6 months of oral treatment with clodronate reduced the migration of the NexGen total knee prosthesis during the first postoperative year, as measured by radiostereometry (RSA). We now report the 4-year results.

Methods This was a double-blind randomized study, using RSA with maximal total point motion (MTPM).

Results With analysis according to the “intention to treat” principle, the only remaining difference between the groups at 4 years was reduced rotation around the transverse axis (a secondary variable) in the clodronate group. However, 3 patients (all clodronate) did not take any tablet after surgery. If they are excluded, there was an almost statistically significant difference between the groups at 4 years regarding MTPM from baseline, with the clodronate group showing 25% less migration. From 1 to 4 years, there was no difference in migration rate by MTPM, but there was a continuous increase in rotation around the transverse axis in the controls, which differed from the clodronate group. There were no cases of aseptic loosening. 2 patients had migration of more than 1.3 mm from baseline to 4 years; neither of them had taken clodronate. The others had migration of less than 0.9 mm.

Interpretation Because migration was clearly reduced by clodronate during the first postoperative year, and there was still a difference at 4 years when analyzed per protocol, it appears likely that this treatment can diminish the risk of loosening. The difference in the number of outliers also points in this direction, and may be more relevant than mean migration values.     

腰椎内固定融合术后邻近节段退变的影响因素

目的探讨腰椎内固定融合术后邻近节段退变的影响因素。方法对1998年3月至2002年5月33例行腰椎内固定融合术的病例进行随访研究,观察其术后邻近节段退变的发生率、发生年龄、部位、影像学特点以及临床表现,对是否“悬浮固定”、内固定融合范围、不同邻近节段退变的风险进行对比。结果33例患者随访34～82个月,平均4年7个月。发现影像学上有退变表现10例（占30．3％）,10例中有9例退变发生在头侧节段。发生邻近节段退变以60岁以上患者为主。是否进行“悬浮固定”对内固定融合术后邻近节段退变的影响无统计学差异。多节段融合术后较单节段融合术后邻近节段退变有增多的趋势。L2／L3作为邻近节段时退变风险较高,而L5／L1,作为邻近节段退变风险较低。结论头侧邻近节段较尾侧节段更容易发生退变。如果L2／L3可能作为邻近节段,术前有退变表现,术中需将其进行固定融合,而如果L5／S1在术前没有明显退变证据,则不需要将其进行固定融合。腰椎内固定融合时,尽量避免长节段固定融合。