Intraoperative assessment of resected condyle thickness in total knee arthroplasty

Purpose

The purpose of this study was to assess the use of resected condyle thickness measurement, obtained with caliper, when verifying the accuracy of distal femoral bone resection in total knee arthroplasty.

Methods

Fifty-two total knee arthroplasties were performed to treat osteoarthritis with varus knee. The difference of caliper-measured thickness of resected medial and lateral femoral condyles after removal of cartilage from the lateral condyle was compared with radiographically measured values. The preoperative planned valgus cut angles and the postoperative femoral component valgus angles were compared.

Results

The difference of radiograph-measured thickness averaged 2.4 ± 2.2 mm and the difference of caliper-measured thickness averaged 2.0 ± 2.1 mm (r = 0.735, P < 0.001). The postoperative femoral component valgus angle averaged 4.8° ± 1.6° (range, 2.0°–7.6°). The difference between the valgus cut angle and femoral component valgus angle averaged ?0.3° ± 1.5°.

Conclusions

The confirmation of correspondence between the caliper-measured and radiographically measured thickness of resected condyles could verify the accuracy of distal femoral bone resection in total knee arthroplasty.

Level of evidence

III.     

The coronal alignment after medial unicompartmental knee arthroplasty can be predicted: usefulness of full-length valgus stress radiography for evaluating correctability

Purpose

We aimed to clarify whether the coronal alignment after medial unicompartmental knee arthroplasty (UKA) is predictable using preoperative full-length valgus stress radiography.

Methods

Thirty-seven consecutive patients with a mean age of 71.5 ± 7.0 years awaiting medial UKA were recruited. Full-length weight-bearing radiographs of the lower limbs were obtained pre- and postoperatively. Preoperative full-length valgus stress radiography in the supine position was also performed, and the transition of the hip-knee-ankle angle (HKAA) and the weight-bearing ratio were assessed. The tibia first cut technique was used, and the distal femur was cut parallel to the cutting surface of the proximal tibia during surgery.

Results

The mean postoperative HKAA was 2.0° ± 2.1° varus, and the mean weight-bearing ratio was 43.1 ± 7.7 %; each of these parameters demonstrated significantly strong correlations with the values on the preoperative valgus stress radiographs (p < 0.01), while the correlation between the postoperative alignment and the preoperative standing alignment without stress was moderate (p < 0.01). The postoperative alignment was slightly undercorrected compared to that observed on the valgus stress radiographs (p < 0.05), and no knees exhibited evident overcorrection compared to that on the valgus stress radiographs.

Conclusion

Preoperative valgus stress radiography is useful for evaluating the correctability of varus deformities and predicting the postoperative coronal alignment. For clinical relevance, performing preoperative valgus stress radiography would help to more precisely select patients and, when combined with the tibia first cut technique, aid in achieving the expected knee alignment and avoid severe undercorrection or overcorrection.

Level of evidence

Diagnostic study, Level II.     

Unconstrained arthroplasty in type II valgus knees: posterior stabilized or cruciate retaining?

Purpose

Type II valgus knees are defined by medial collateral ligament laxity. This paper studies the results of posterior stabilized (PS) and cruciate retaining (CR) knee implants in type II valgus knees.

Methods

From 1999 to 2009, there were 100 type II valgus knees in 95 patients eligible for study (63 PS, 37 CR). Patients had prospectively collected clinical data up to 2 years after surgery.

Results

At 24 months after surgery, the CR group had reduced range of motion (PS: median 126.0°, CR: median 114°; n.s.) and a marginally but statistically significant increased valgus alignment (PS: median 5°, CR: median 6°; p = 0.011). Despite this, both groups produced equal and marked improvements in SF-36, function score and knee score of the Knee Society score, and Oxford knee score.

Conclusions

Overall, both PS and CR implants performed equally well in type II valgus knees at 24 months post-operatively. Further longer-term studies would be warranted to assess for late instability.

Level of evidence

Retrospective, Level III.     

Partial restoration of knee kinematics in severe valgus deformity using the medial-pivot total knee arthroplasty

Purpose

The objectives of the study were to examine knee kinematics in knees with severe valgus deformities and to compare pre- and post-operative knee kinematics for the same subjects implanted with medial-pivot total knee arthroplasty (TKA).

Methods

Seven subjects with severe valgus deformities due to osteoarthritis (OA) or rheumatoid arthritis (RA) were enrolled in the prospective study. Prior to TKA, three-dimensional (3D) kinematics were assessed by 3D to 2D registration technique using the image matching software ‘Knee Motion’, under in vivo, weight-bearing conditions. Postoperatively, each subject again performed the same motion under fluoroscopic surveillance.

Results

Preoperative kinematics demonstrated external rotation of tibias from extension to flexion, and small posterior femoral translations dominated in the medial condyle associated with anterior slides during partial range of motion. Postoperatively, these non-physiological tibial rotations were restored, and most subjects exhibited small internal rotations of tibias. On average, preoperative tibial internal rotation was ?4.7° ± 7.6° from full extension to maximum flexion, and the angle was 4.8° ± 3.1° postoperatively (p = 0.01). In addition, small amounts of posterior translation of the lateral condyle and anterior translation of the medial condyle were confirmed in most subjects postoperatively.

Conclusions

The study showed that the preoperative kinematic pattern established in severe valgus deformity was different from the physiological knee pattern. In addition, post-operative results suggest that the non-physiological kinematics were partially restored after TKA by using the prosthesis design even in the absence of the posterior cruciate ligament (PCL) and the cam–post mechanism.

Level of evidence

II.     

The effect of lateral opening wedge distal femoral osteotomy on medial knee opening: clinical and biomechanical factors

Purpose

The case of a patient with knee valgus and instability due to combined ACL–MCL laxity who underwent lateral opening wedge distal femoral osteotomy (DFO) is presented. The symptoms of instability resolved following the surgery. It was unclear whether the increase in valgus stability was related only to a decrease in valgus moments during stance or also to a medial tensioning effect. We therefore performed a laboratory cadaveric study. The purpose of this study was to examine whether after MCL and ACL sectioning, lateral opening wedge DFO would result in decrease in medial opening under static conditions of valgus stress.

Methods

Medial knee opening under valgus load of 9.8 Nm was tested in 8 cadaveric specimens in scenarios of MCL and ACL sectioning and compared before and after performing lateral opening wedge DFO.

Results

When the superficial MCL was sectioned, medial knee opening in 30° flexion decreased after lateral opening wedge DFO compared to medial opening before the osteotomy (i.e. from 6.5 ± 0.5° to 5.6 ± 0.5°, p = 0.01). When the superficial MCL, deep MCL, and ACL were all sectioned, medial knee opening in extension decreased after lateral opening wedge DFO compared to medial opening before the osteotomy but this was not significant (i.e. from 6.8 ± 0.5° to 6.1 ± 0.5°, p = n.s.).

Conclusion

In superficial MCL-transected knees, medial laxity at 30° of knee flexion decreased after lateral opening wedge DFO. However, the clinical relevance of the laxity decrease observed remains uncertain since the reduction was small in magnitude.

Level of evidence

Controlled laboratory study.     

Alignment does not influence cartilage T2 in asymptomatic knee joints

Purpose

To investigate whether the static knee alignment affects articular cartilage ultrastructures when measured using T2 relaxation among asymptomatic subjects.

Methods

Both knee joints (n = 96) of 48 asymptomatic volunteers (26 females, 22 males; 25.4 ± 1.7 years; no history of major knee trauma or surgery) were evaluated clinically (Lysholm, Tegner) and by MRI (hip–knee–ankle angle, standard knee protocol, T2 mapping). Group (n = 4) division was as follows: neutral (<1° varus/valgus), mild varus (2°–4° varus), severe varus (>4° varus) and valgus (2°–4° valgus) deformity with n = 12 subjects/group; n = 24 knees/group. Regions of interest (ROI) for T2 assessment were placed within full-thickness cartilage across the whole joint surface and were divided respecting compartmental as well as functional joint anatomy.

Results

Leg alignment was 0.7° ± 0.5° varus among neutral, 3.0° ± 0.6° varus among mild varus, 5.0° ± 1.1° varus among severe varus and 2.5° ± 0.7° valgus among valgus group subjects and thus significantly different. No differences between the groups emerged from clinical measures. No morphological pathology was detected in any knee joint. Global T2 values (42.3 ± 2.3; 37.7–47.9 ms) of ROIs placed within every knee joint per subject were not different between alignment groups or between genders, respectively.

Conclusion

Static frontal plane leg malalignment does not affect cartilage ultrastructure among young, asymptomatic individuals as measured by T2 quantitative imaging.

Level of evidence

Cross-sectional study, Level II-III.     

Diagnostic performance of MRI measurements to assess hindfoot malalignment. An assessment of four measurement techniques

Objective

To investigate the ability of coronal non-weight-bearing MR images to discriminate between normal and abnormal hindfoot alignment.

Methods

Three different measurement techniques (calcaneal axis, medial/lateral calcaneal contour) based on weight-bearing hindfoot alignment radiographs were applied in 49 patients (mean, 48 years; range 21–76 years). Three groups of subjects were enrolled: (1) normal hindfoot alignment (0°–10° valgus); (2) abnormal valgus (>10°); (3) any degree of varus hindfoot alignment. Hindfoot alignment was then measured on coronal MR images using four different measurement techniques (calcaneal axis, medial/lateral calcaneal contour, sustentaculum tangent). ROC analysis was performed to find the MR measurement with the greatest sensitivity and specificity for discrimination between normal and abnormal hindfoot alignment.

Results

The most accurate measurement on MR images to detect abnormal hindfoot valgus was the one using the medial calcaneal contour, reaching a sensitivity/specificity of 86 %/75 % using a cutoff value of >11° valgus. The most accurate measurement on MR images to detect abnormal hindfoot varus was the sustentaculum tangent, reaching a sensitivity/specificity of 91 %/71 % using a cutoff value of <12° valgus.

Conclusion

It is possible to suspect abnormal hindfoot alignment on coronal non-weight-bearing MR images.

Key Points

? Abnormal hindfoot alignment can be identified on coronal non-weight-bearing MR images. ? The sustentaculum tangent was the best predictor of an abnormally varus hindfoot. ? The medial calcaneal contour was the best predictor of a valgus hindfoot.     

Femoral bone and cartilage wear is predictable at 0° and 90° in the osteoarthritic knee treated with total knee arthroplasty

Purpose

Kinematically aligned total knee arthroplasty (TKA) positions the femoral component at the natural angle and level of the distal (0°) and posterior (90°) joint line. This technique applies referencing guides at 0° and 90° that are adjusted to compensate for wear and kerf and perform resections equal in thickness to the femoral component. Knowing whether femoral bone and cartilage wear is predictable would assist in establishing general guidelines for adjusting the resection level of these two referencing guides. This study tests the hypothesis that femoral bone and cartilage wear is predictable at 0° and 90° in the varus and valgus osteoarthritic knee treated with TKA.

Methods

The study consists of 205 patients and 208 knees with Kellgren–Lawrence Grade 3 or 4 osteoarthritis and treated with a TKA. Each knee had a narrow slice (2 mm) preoperative 1.5 tesla magnetic resonance image in the sagittal plane. Femoral bone and cartilage wear at 0° and 90° was computed from best-fit circles superimposed on the peripheral boundary of the subchondral bone on the medial and lateral femoral condyles.

Results

Overall, 99.5 % of knees had minimal bone wear (<1 mm) at 0° and 90°. In the 74 % (154 of 208) of knees with a varus deformity, 92 % at 0° and 2 % at 90° had >1 mm cartilage wear on the medial femoral condyle. In the 26 % (54 of 208) of knees with a valgus deformity, 78 % at 0° and 55 % at 90° had ≥1 mm cartilage wear on the lateral femoral condyle.

Conclusions

As a general guideline, adjustment for femoral bone wear is rarely required when performing kinematically aligned TKA. Most osteoarthritic knees require adjustment of the distal referencing guide to compensate for cartilage wear on the medial femoral condyle in the varus knee and the lateral femoral condyle in the valgus knee. Adjustment of the posterior referencing guide is required in about half of valgus osteoarthritic knees to compensate for lateral cartilage wear at 90°. Knowing that bone wear is rare and cartilage wear is predictable in varus and valgus Kellgren–Lawrence Grade 3 or 4 osteoarthritic knees helps establish general guidelines for adjusting the distal and posterior femoral referencing guides to restore the natural angle and level of the femoral joint lines when performing kinematically aligned TKA with generic instruments.

Level of evidence

IV.     

Is valgus unloader bracing effective in normally aligned individuals: implications for post-surgical protocols following cartilage restoration procedures

Purpose

Utilizing valgus unloader braces to reduce medial compartment loading in patients undergoing cartilage restoration procedures may be an alternative to non-weightbearing post-operative protocols in these patients. It was hypothesized that valgus unloader braces will reduce knee adduction moment during the stance phase in healthy subjects with normal knee alignment.

Methods

Gait analysis was performed on twelve adult subjects with normal knee alignment and no history of knee pathology. Subjects were fitted with an off-the-shelf adjustable valgus unloader brace and tested under five conditions: one with no brace and four with increasing valgus force applied by the brace. Frontal and sagittal plane knee angles and external moments were calculated during stance via inverse dynamics. Analyses of variance were used to assess the effect of the brace conditions on frontal and sagittal plane joint angles and moments.

Results

With increasing tension in the brace, peak frontal plane knee angle during stance shifted from 1.6° ± 4.2° varus without the brace to 4.1° ± 3.6° valgus with maximum brace tension (P = 0.02 compared with the no brace condition). Peak knee adduction moment and knee adduction impulse decreased with increasing brace tension (main effect of brace, P < 0.001). Gait velocity and sagittal plane knee biomechanics were minimally affected.

Conclusion

The use of these braces following a cartilage restoration procedure may provide adequate protection of the repair site without limiting the patient’s mobility.

Level of evidence

Therapeutic prospective comparative study, Level II.     

Relationship between the tibial anteroposterior axis and the surgical epicondylar axis in varus and valgus knees

Purpose

Proper rotational alignment in total knee arthroplasty (TKA) is essential for successful outcomes. The surgical epicondylar axis (SEA) has been frequently used to determine the femoral rotational alignment, and the anteroposterior (AP) axis of the tibia described in previous study has been introduced as a line perpendicular to the SEA in healthy knees. However, the rotational relationship between the distal femur and the proximal tibia would vary between normal and osteoarthritic knees, and a question remains whether the rotational relationship between the SEA and the AP axis of the tibia would be the same between normal and osteoarthritic knees. This study aims to determine whether the AP axis of the tibia is actually perpendicular to the SEA and useful for the tibial rotational alignment also in osteoarthritic knees.

Methods

Preoperative computed tomography scans on 25 varus and 25 valgus knees undergoing TKA were studied. The SEA and the AP axis of the tibia were identified using a three-dimensional software, and the angle between the line perpendicular to the projected SEA and the AP axis was measured.

Results

The AP axis of the tibia was 1.7° ± 4.3° and 2.0° ± 4.0° internally rotated relative to the line perpendicular to the SEA in the varus and valgus groups, respectively.

Conclusions

The AP axis of the tibia was, on average, perpendicular to the SEA in both varus and valgus knees. The AP axis would be useful for setting the tibial component with minimal rotational mismatch.

Level of evidence

IV.     

The minimally invasive far medial subvastus approach for total knee arthroplasty in valgus knees

Purpose

The lateral approach in the valgus knee asks for a lot of soft tissue releases during the arthrotomy. The hypothesis of this study was that the far medial subvastus approach could be used in valgus knees and would guarantee both functional and radiological good to excellent results.

Methods

This is a retrospective study on 78 patients (84 knees) undergoing primary total knee arthroplasty (TKA) for type I or II fixed valgus knees. The mean (SD) preoperative mechanical alignment was 187° (4°) HKA angle. Functional recovery, pain, tourniquet times, necessary soft tissue releases as well as radiological alignment were measured.

Results

The Knee Score improved significantly from 45 (10) to 90 (10) (P < 0.05) and the function score improved as well from 35 (20) to 85 (10) (P < 0.05). Flexion improved from 110° (10°) to 137° (8°). Hospital stay was 4 (1.2) days. Alignment was corrected to 181° (1.5°) HKA angle with a postoperative joint line shift of +2.8 (3.2) mm. No clinical instability, as evaluated by the senior author, or osteolytic lines was observed at minimal one-year radiological follow-up.

Conclusion

The far medial subvastus approach is an excellent approach to perform Krackow type I and II TKA with primary PS implants.

Level of evidence

IV.     

Flexion and extension laxity after medial, mobile-bearing unicompartmental knee arthroplasty: a comparison between a spacer- and a tension-guided technique

Purpose

In a mobile-bearing unicompartmental knee arthroplasty (UKA), stability is of utmost importance to promote knee function and to prevent dislocation of the insert. Gap balancing can be guided by the use of spacers or a tensioner. The goal of this study is to compare laxity of a tension-guided implantation technique versus a spacer-guided technique for medial UKA with a mobile bearing. Also clinical function was compared between the groups.

Methods

The tension-guided UKA system (BalanSys?, Mathys Ltd, Bettlach, Switzerland) was compared with a retrospective group with a spacer-guided system (Oxford, Biomet Ltd, Bridgend, UK). A total of 30 tension-guided medial UKAs were implanted and compared with 35 spacer-guided medial prostheses. In both groups, valgus laxity was measured at least 4 months postoperatively in extension and 70° flexion using stress radiographs. Knee Society Scores (KSS) were obtained at the 6-month follow-up.

Results

Valgus laxity in flexion was significantly higher in the tension-guided group compared with the spacer-guided group: 3.9° (SD 1.8°) versus 2.4° (SD 1.2°), respectively, P < 0.001). In extension, valgus laxity was significantly different: 1.8° (SD 1.0°) in the tension-guided group compared with 2.7° (SD 0.9°) in the spacer-guided group (P < 0.001). There was no significant difference between the KSS for the two groups (n.s.).

Conclusions

The tensor-guided system resulted in significantly more valgus laxity in flexion compared with the spacer-guided system. However, in extension, the situation was reversed: the tension-guided system resulted in less valgus laxity than the spacer-guided system. Clinically, there were no differences between the groups. The valgus laxity found with the spacer-guided system better approximates the valgus laxity values of the healthy elderly.

Level of evidence

Lower quality prospective cohort study (<80 % follow-up, patients enrolled at different time points in disease), Level II.     

Effect of foot rotation on the mechanical axis and correlation between knee and whole leg radiographs

Purpose

The purposes of this study were (1) to evaluate the foot rotational effects on local and whole leg alignment and (2) to confirm the correlation between local and whole leg alignment. The hypotheses of this study were that (1) the alignment would become varus if the rotation of the foot changes from internal to external rotation, and (2) there would be some correlation between local and whole leg radiographs, and local knee radiographs could then be used indirectly for the assessment of whole leg alignment in patients with bilateral medial compartment knee osteoarthritis.

Methods

A total of 80 lower limbs with genu varum of patients who complained of medial knee pain were examined. The standing anterior–posterior view of whole leg radiographs was taken in the four foot positions, and a custom-made foot plate was used for the attainment of accurate radiographs: feet straight ahead with foot contact at the medial side (R: routine), feet straight ahead at shoulder width (N: neutral), 30° external rotated (ER) and 15° internal rotated (IR) position. In order to obtain a local radiograph of the knee, we took only whole leg radiographs and selected the area of interest on the whole leg radiograph. We evaluated the total width of the tibia plateau (Total), the length of the weight-bearing line, the ratio of weight-bearing line/Total and femorotibial angle (FTA).

Results

The absolute value of weight-bearing line was shifted laterally in the 30° ER position and shifted medially in the 15° IR position compared to the neutral position (1.8 mm lateral and 0.2 mm medial in the WLR; 3.5 mm lateral and 3 mm medial in the local radiograph). Significant statistical differences were observed in the local knee weight-bearing line; however, no significant statistical differences were observed in the weight-bearing line of the whole leg radiograph (n.s.). Results of the % (weight-bearing line/Total) were similar to those of weight-bearing line. The FTA of the local radiograph showed statistical differences, and it showed more valgus in the 30° ER position. In the correlation analysis between whole leg radiograph and local knee radiograph, moderate correlation (correlation coefficient = 0.67) was observed; however, significant statistical differences were observed in the comparison of weight-bearing line and % weight-bearing line/Total (p < 0.01 and < 0.01, respectively) between local knee and whole leg radiograph.

Conclusions

Foot position of ER could show less varus alignment and the reverse could occur in the IR position, compared to the neutral foot position. The severity of varus alignment could be underestimated in the local radiograph, compared with that of whole leg radiograph.

Level of evidence

Cohort study (diagnosis), Level II.     

Non-anatomical capsular closure of a standard parapatellar knee arthrotomy leads to patellar maltracking and decreased range of motion: a cadaver study

Purpose

A parapatellar approach disrupts the medial soft tissue stabilizers of the patella. We hypothesized that soft tissue realignment during arthrotomy closure of native cadaveric knees influences patellar kinematics leading to decreased range of motion.

Methods

Parapatellar arthrotomy was performed in seven native human cadaveric knees that did not contain arthroplasty components. Capsular closure was performed with figure-of-eight sutures in five different positions for each specimen. The capsule was closed anatomically, and then shifted 1.5 or 3 cm distal, or 1.5 or 3 cm proximal relative to surgical markings of the patellar poles. In each closure position, real-time patellar kinematics and range of motion were recorded using a navigation system with patellar tracking function.

Results

Maximum knee flexion was significantly reduced with closure shifted 3 cm proximal (133° ± 8.2°, p < 0.001) or distal (139° ± 6.4°, p < 0.05) compared to anatomical closure (147° ± 4.1°). All closure positions significantly influenced patellar rotation at 45°, 90°, and 120° of flexion (p < 0.001). Closure 1.5 or 3 cm distal increased lateral patellar shift relative to the mechanical axis (p < 0.01). Patellar tilt was significantly decreased at 90° and 120° by closure 3 cm distal (p < 0.01) and at 120° when closed 1.5 cm distal (p < 0.05).

Conclusions

Imprecise arthrotomy closure significantly impacted patellar kinematics and passive range of motion. Therefore, every effort should be made to provide anatomical closure of the extensor mechanism to preserve native patellar movement kinematics.

Level of evidence

V.     

The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty

Purpose

The aim of this study was to investigate the post-operative radiological outcomes of patient-specific instrumentation (PSI) surgery versus conventional total knee arthroplasty (TKA).

Methods

Sixty patients scheduled for a primary TKA were prospectively divided into PSI or conventional technique. Coronal and sagittal radiographic long limb films were taken post-operatively. The accepted values for normal alignment were 180° ± 3° for hip-knee-ankle angle; 90° ± 3° for coronal femoral component angle or coronal tibia component angle; 0° to 3° flexion for sagittal femoral component angle and 0° to 7° posterior slope for sagittal tibia component angle.

Results

For hip-knee-ankle angle, there were 21 % more outliers in the PSI group compared to the conventional group (p = 0.045). Most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group (p = 0.045). For implant placement, there was no difference in the proportion of outliers between the two groups. There was also no difference in the duration of surgery.

Conclusions

This study showed that PSI surgery is associated with a larger proportion of outliers for lower limb alignment. PSI surgery as an alternative to conventional TKA is not advisable.

Level of evidence

II.     

A case series of lateral opening wedge high tibial osteotomy for valgus malalignment

Introduction

Lateral opening wedge high tibial osteotomy is a rarely employed surgical technique used for the treatment of lateral knee pain and degeneration in the setting of genu valgum. There exists little evidence of the suitability of this procedure for patients requiring osteotomies with a small correction.

Materials and methods

A case series of 23 patients (24 knees) undergoing lateral opening wedge high tibial osteotomy with a minimum follow-up of 2 years was performed between 2002 and 2008. A surgical technique avoiding the need for fibular osteotomy is described. Adverse events, patient-reported outcomes and radiographic measures of alignment were assessed at baseline, at 6 months postoperatively, and at time of final follow-up. A subgroup of 12 patients also underwent 3D gait analysis at the same time points.

Results

The mean follow-up was 52 months (±20.4). Statistically and clinically significant improvements were identified in the lower extremity functional scale [mean change (95 %CI) = 10 (2.4, 17.6)], and in the knee injury and osteoarthritis outcome score [mean change (95 %CI) = 10.9 (0.5, 21.4)]. Mechanical axis changed from 2.4 ± 2.4° valgus to 0 ± 2.6° varus (p<0.001), anatomical axis from 6.9 ± 2.8° to 4.7 ± 2.5° valgus (p < 0.001), with weight-bearing line offset changing from 60.2 ± 11.4 % to 49.5 ± 12.4 % (p < 0.001). Change in lateral tibial slope, from 6.5 ± 2.2° to 7.5 ± 2.3°, was very small and not statistically significant (n.s.). The peak knee adduction moment during gait significantly increased [mean change (95 %CI) = 0.72 %BW*Ht (0.42, 1.02), suggesting a medial shift in dynamic knee joint load. Two patients underwent total knee arthroplasty during the study period.

Conclusions

Lateral opening wedge high tibial osteotomy is a viable surgical option for patients with lateral knee pain and valgus malalignment requiring small degrees of correction.

Level of evidence

IV.     

The shape and orientation of the trochlea run more parallel to the posterior condylar line than generally believed

Purpose

This study was set up to identify the native trochlear geometry and define its relationship with the rotational landmarks of the distal femur.

Methods

The rotational landmarks of the distal femur were analysed on CT-scans of 281 patients with end-stage knee osteoarthritis.

Results

The anterior trochlear line (ATL) was on average 4.3° (SD 3.3°) internally rotated relative to the surgical transepicondylar axis (sTEA). The ATL was on average 2.1° (SD 3.0°) internally rotated relative to the posterior condylar line (PCL). The relationship between the ATL and the sTEA was statistically different in the different coronal alignment groups (p = 0.004): 3.9° (SD 3.0°) in varus knees, 4.0° (SD 2.9°) in neutral knees and 5.4° (SD 3.8°) in valgus knees. The lateralisation of the trochlea, represented by the distance between the perpendicular to PCL and the perpendicular to the posterior parallel line to the sTEA, was on average 2.2 mm (SD 1.8 mm).

Conclusion

The ATL was on average 4.3° (SD 3.3°) internally rotated relative to the sTEA and 2.1° (SD 3.0°) internally rotated relative to the PCL. The ATL is more externally orientated in varus knees and more internally rotated in valgus knees. The trochlear groove is lateralised by only 2.2 mm when the femoral component is externally rotated.

Level of evidence

III.

     

Intermediate ray deficiency—a new type of lower limb hypoplasia

Objective

Diagnosis of fibular hemimelia is based on the identification of absence or shortening of the fibula in relation to the tibia. Despite the existence of different classifications of this congenital deficiency, certain morphological forms defy proper classification. One such form is absence of foot rays with leg shortening in the presence of an entire fibula. In these cases, foot morphology suggests that central foot rays, not lateral ones, are affected by the deficiency; thus justifying the hypothesis concerning the existence of a separate type of hypoplasia, which may be named “intermediate ray deficiency” (IRD).

Materials and methods

Nine patients with IRD, with an average age of 9.4 years at diagnosis (2.9–15), were analyzed. Clinical and radiographic parameters of the leg and foot were recorded according to the Stanitski classification of fibular hemimelia. The position of the lateral and medial malleoli was assessed. Axial alignment was analyzed according to the Paley method.

Results

The number of foot rays in eight cases was 4, while in one case, it was 3. Talocalcaneal synostosis was observed in seven cases. The shape of the ankle joint was spherical in six cases, horizontal in two cases and valgus in one case. The position of the lateral malleolus was slightly higher compared to normal. An average functional leg length discrepancy was 4.4 cm. The average percentage of fibular shortening was 9.5 %, tibial shortening 8.7 % and femoral shortening 3.3 %. In all of the cases, slight knee valgus was observed on the femoral level (average 3.3°) and tibial level (average 2.0°). As a result, criteria for IRD diagnosis were proposed.

Conclusion

“Intermediate ray deficiency” might be defined as a separate type of lower limb hypoplasia.     

Rotational alignment of the distal femur: anthropometric measurements with CT-based patient-specific instruments planning show high variability of the posterior condylar angle

Purpose

Finding the anatomical landmarks used for correct femoral axial alignment can be difficult. The posterior condylar line (PCL) is probably the easiest to find during surgery. The aim of this study was to analyse whether a predetermined fixed angle referencing of the PCL could help find the surgical epicondylar axis (SEA) and this based on a large CT database with enough Caucasian diversity to be representable.

Methods

A total of 2,637 CT scans and 3D reconstructions from patients on four continents, executed for preoperative planning and creation of patient-specific instrumentation, were used to perform anthropometric measurements and to measure the posterior condylar angle (PCA) between the surgical epicondylar angle and the PCL.

Results

The mean (SD) PCA was 4° (1.4°) of external rotation. A significant correlation was found between more external rotation of the SEA and more proximal varus of the tibia or more distal valgus of the femur. For 59 % of the study population, 4° external rotation from the PCL would be the right amount of axial rotation to align the femoral component in line with the SEA. Nine per cent needs less, and 32 % needs more than 4° of axial rotation. On 105 (4 %) CT-based 3D models, external rotation between 7° and 11° was measured and 77 (73 %) of those cases were in varus or neutral alignment. In 132 patients, bilateral measurements were available and 94 (71 %) had rotation within 1° of the opposite side. This last finding underlines that there is even an intra-individual difference in distal femoral anatomy that can range from 1° to 5°.

Conclusions

This study was performed on a very large anthropometric CT and 3D models database and showed that there is a 41 % risk of malalignment if a fixed PCA referenced of the PCL is used in total knee arthroplasty. The clinical importance of this study is the observation that femoral axial anatomy is individual and also that it is determined by the tibial anatomy. A group of patients needs more than the average external rotation because they have more distal femoral valgus with dysplastic condyles or more proximal tibial varus with a bigger medial condyle.

Level of evidence

III.     

Use of the iPhone for radiographic evaluation of hallux valgus

Objective

The purpose of this study was to compare the measurements made using a smartphone accelerometer and computerized measurements as a reference in a series of 32 hallux valgus patients.

Materials and methods

Two observers used an iPhone to measure the hallux valgus angle (HVA), intermetatarsal angle (IMA), and distal metatarsal articular angle (of anteroposterior foot radiographs in 32 patients with symptomatic hallux valgus on a computer screen. Digital angular measurements on the computer were set as the reference standard for analysis and comparison. The difference between computerized measurements and all iPhone measurements, and the difference between the first and second iPhone measurements for each observer were calculated. Inter- and intraobserver reliability of the smartphone measurement method was also tested.

Results

The variability of all measurements was similar for the iPhone and the computer-assisted techniques. The concordance between iPhone and computer-assisted angular measurements was excellent for the HVA, IMA, and DMAA. The maximum mean difference between the two techniques was 1.25?±?1.02° for HVA, 0.92?±?0.92° for IMA, and 1.10?±?0.82° for DMAA. The interobserver reliability was excellent for HVA, IMA, and DMAA. The maximum mean difference between observers was 1.31?±?0.89° for HVA, 0.90?±?0.92° for IMA, and 0.78?±?0.87° for DMAA. The intraobserver reliability was excellent for HVA, IMA, and DMAA.

Conclusions

We conclude that the Hallux Angles software for the iPhone can be used for measurement of hallux valgus angles in clinical practice and even for research purposes. It is an accurate and reproducible method.