A stand-alone lateral condyle-elevating trochlear osteotomy leads to high residual instability but no excessive increase in patellofemoral osteoarthritis at 12-year follow-up.

PURPOSE AND HYPOTHESIS: Trochlear osteotomy is a rarely performed procedure, only indicated in selected cases. Due to its nature, it can potentially lead to cartilage damage and subsequent early osteoarthritis. Satisfactory short-term results from lateral condyle-elevating osteotomy have previously been reported. The long-term effects of this procedure on clinical outcomes, patellar stability and radiological osteoarthritis are reported here. METHODS: Sixteen patients (19 knees) with patellar instability due to trochlear dysplasia were included. An isolated lateral condyle-elevating trochlear osteotomy was performed between 1995 and 2002. All patients were re-examined at a minimum of 12-year follow-up. Three patients were lost to follow-up, and one patient underwent a patellofemoral arthroplasty 3 years post-operatively due to progressive osteoarthritis. Complete follow-up was therefore available in 12 patients (15 knees). Recurrent instability, VAS pain, WOMAC, Lysholm and Kujala scores were used as outcome measures. Radiological osteoarthritis was recorded using the Iwano and the Kellgren-Lawrence classifications. A repeated-measures ANOVA was used to test for repeated measures (pre-operative, 2-year and final follow-up), and Spearman's correlation coefficient for relationships between osteoarthritis and functional scores. RESULTS: At final follow-up, VAS pain showed a non-significant improvement from 52 to 25, and the median Kujala score was 78. Median Lysholm (54-71, p = 0.021) and WOMAC (78-96, p = 0.021) scores improved from the pre-operative assessment to final follow-up. There was no significant difference observed between clinical scores at the 2-year and final follow-up. Residual patellar instability was reported in four out of 15 knees. Three knees showed no patellofemoral osteoarthritis, eight knees had grade 1 and four knees grade 2. No correlation between VAS pain, Lysholm, WOMAC or Kujala scores and osteoarthritis could be identified (n.s.). CONCLUSION: A stand-alone lateral condyle-elevating trochleoplasty results in the significant improvement of most clinical scores; however, when performed as a stand-alone procedure, it leads to a high percentage of residual instability. In contrast to general belief, the development of patellofemoral osteoarthritis at 12-year follow-up did not exceed the findings from other trochleoplasty case series. LEVEL OF EVIDENCE: Case series with no comparison group, Level IV.

Radiological characteristics of the knee joint in nail patella syndrome.

AIM: Nail patella syndrome (NPS) is a skeletal dysplasia with patellofemoral dysfunction as a key symptom. We present the first in-depth radiological evaluation of the knee in a large series of NPS patients and describe the typical malformations. PATIENTS AND METHODS: Conventional radiological examination of 95 skeletally mature patients with NPS was performed. Patellar morphology was classified according to the Wiberg classification as modified by Baumgartl and Ficat criteria, and trochlear shape was classified according to the Dejour classification. RESULTS: Patellar aplasia was present in 4/90 (4%), and patellar hypoplasia in 77/90 (86%) of patients. The prevailing patellar shapes were type III, type IV and Hunter's cap. No patellar shape genotype-phenotype association could be found. The malformations of the distal femur comprised shortening of the lateral femoral condyle in 46 out of 84 patients (55%), with a prominent anterior surface of the lateral femoral condyle in 47 out of 84 patients (56%) and a flat anterior surface of the medial femoral condyle in 78 out of 85 patients (92%). The trochlea was type A1 according to the Dejour classification in 79 out of 85 patients (93%). CONCLUSION: An easily recognisable characteristic quartet of malformations consisting of patellar aplasiaor hypoplasia and the malformations of the distal femur was found in 22 out of 81 patients (27%), with the majority displaying at least three malformations. TAKE HOME MESSAGE: The distinct malformations of the knee in nail patella syndrome are easily recognisable on conventional radiographs and lead to the correct interpretation of the aberrant morphology which is essential in the treatment of these patellofemoral disorders.

Nail patella syndrome: Knee symptoms and surgical outcomes. A questionnaire-based survey.

BACKGROUND: Patellofemoral instability and dysfunction are frequent symptoms in Nail patella syndrome (NPS). In this article, the first large series of NPS patients is presented in which these knee symptoms were assessed using validated outcome scores. Additionally, the need for surgical interventions, percentage of patients who received surgical treatment and patient reported outcomes are reported. METHODS: A questionnaire based survey was conducted in 139 Dutch NPS patients. Symptoms of the knees were assessed by the Knee injury and Osteoarthritis Outcome Score (KOOS) and Kujala knee score. The questionnaire addressed whether surgical intervention was currently considered, history of past surgeries, type of surgical procedures performed and results of these procedures. RESULTS: Response rate was 74%. Mean KOOS (73.04) and Kujala (74.01) scores showed a wide range and variability between patients. Patellofemoral instability was present in 48.5% of patients. Surgical intervention was currently considered by 12% of patients. Their KOOS and Kujala scores were significantly lower compared to those not considering surgery and they experienced more patellar instability. Surgery was performed on 31 knees in 23 patients. KOOS and Kujala scores were lower in surgically treated versus nonoperated patients but no difference in patellar instability was present. An improvement in pain in 87% and in function in 30% of knees was reported after surgery. Patient satisfaction with the surgical results was 61% and 10% was dissatisfied. Patellar realignment procedures showed similar results, although persistent patellar instability was reported in 40% of patients, not different from nonoperated patients. CONCLUSIONS: Knee symptoms in NPS patients vary widely, with patellar instability present in nearly half of the patients. Although surgical treatment appears unfavourable as surgically treated patients have lower KOOS and Kujala scores, the patient reported surgical results are generally good with a high patient satisfaction. LEVEL OF EVIDENCE: Level IV.

A self-centring osteotomy of the tibial tubercle for patellar maltracking or instability: results with ten-years' follow-up.

An increased tibial tubercle-trochlear groove (TT-TG) distance is related to patellar maltracking and instability. Tibial tubercle transfer is a common treatment option for these patients with good short-term results, although the results can deteriorate over time owing to the progression of osteoarthritis. We present a ten-year follow-up study of a self-centring tibial tubercle osteotomy in 60 knees, 30 with maltracking and 30 with patellar instability. Inclusion criteria were a TT-TG ≥ 15 mm and symptoms for > one year. One patient (one knee) was lost to follow-up and one required total knee arthroplasty because of progressive osteoarthritis. Further patellar dislocations occurred in three knees, all in the instability group, one of which required further surgery. The mean visual analogue scores for pain, and Lysholm and Kujala scores improved significantly and were maintained at the final follow-up (repeated measures, p = 0.000, intergroup differences p = 0.449). Signs of maltracking were found in only a minority of patients, with no difference between groups (p > 0.05). An increase in patellofemoral osteoarthritis was seen in 16 knees (31%) with a maximum of grade 2 on the Kellgren-Lawrence scale. The mean increase in grades was 0.31 (0 to 2) and 0.41 (0 to 2) in the maltracking and instability groups respectively (p = 0.2285) This self-centring tibial tubercle osteotomy provides good results at ten years' follow-up without inducing progressive osteoarthritis.

Patellofemoral evaluation with magnetic resonance imaging in 51 knees of asymptomatic subjects.

PURPOSE: The objective of this study is to evaluate patellofemoral joint imaging on magnetic resonance imaging (MRI) in asymptomatic subjects to assess normal values and to test statistical correlation and reliability of MRI scan. METHODS: An analysis of 51 standard MRI examinations was performed. Sulcus angle (SA), patellar axis (PA), lateral patellofemoral angle (LPFA), and lateral patellofemoral length (LPL) were measured. None of the patients suffered from patellofemoral complaints. Patients with patella alta and significant hydrops were excluded. The measurements were assessed with a 2-week interval by two raters under blinded conditions. Statistical analysis was applied by an independent analyst. RESULTS: The mean SA referenced 142.4 ± 6.9°, PA 5.3 ± 3.8°, LPFA 13 ± 4.4°, and LPL 0.8 ± 2.9 mm. Inter-observer variability showed high correlation for LPL and PA, as the repeatability coefficient was high (LPL; 1.49 (LN), 5.7 (ST) and PA; 4.1 (LN), 5.8 (ST). Also, intra-observer variability showed good correlation for LPL and PA. CONCLUSION: The results represent patellofemoral values in the normal population. They indicate that MRI is a reliable imaging technique to determine lateral patellofemoral length and patellar axis. Lateral patellofemoral angle and sulcus angle showed a poor correlation and should not be used for decision making. LEVEL OF EVIDENCE: Development of diagnostic criteria in a consecutive series of patients and a universally applied "gold" standard, Level II.

Coralline hydroxyapatite is a suitable bone graft substitute in an intra-articular goat defect model.

Intra-articular defects can be filled with an autologous bone graft taken from the iliac crest. This can be indicated after trauma or following correcting osteotomy. Patients may encounter donor site morbidity after this procedure. In this in vivo study, we studied if coralline hydroxyapatite (CHA) is a suitable material to replace autologous bone graft to fill a defect in the femoral trochlea of goats. CHA did not evoke any negative reaction in the synovium, and the articular cartilage was comparable to controls. In the bone graft group, we found scattered areas of (enchondral formed) bone. Most bone graft had been resorbed or remodeled, and the scarce remnants were incorporated into new bone. Resorption of CHA was limited or absent and most CHA was surrounded by new bone. In areas with fragmented CHA, close to the joint surface, numerous giant cells were found. The study shows that in this animal model, CHA inserted in a defect that directly communicates with the joint space incorporates into bone. This study did not show any negative effects of CHA in a joint environment.