Patella alta is reduced following MPFL reconstruction but has no effect on quality-of-life outcomes in patients with patellofemoral instability

Abstract

PurposeThe primary purpose of this study was to determine if isolated medial patellofemoral ligament (MPFL) reconstruction for lateral patellofemoral instability altered the patellar height ratio. Secondary purposes were to use disease‐specific quality‐of‐life scores to determine if MPFL reconstruction is as successful in patients with patella alta, compared to those without; and whether the change in the patellar height ratio after MPFL reconstruction is influenced by demographic and clinical factors. MethodsDemographic and clinical data were collected pre‐operatively on 283 patients with recurrent patellofemoral instability. Pre‐operative and 6‐month post‐operative true‐lateral radiographs were assessed to determine the patellar height ratio using the Caton‐Deschamps index. A Caton‐Deschamps index ≥ 1.2 was defined as patella alta. Paired t tests evaluated the effect of MPFL reconstruction on the Caton‐Deschamps index. Using a two‐sample t test, pre‐ and 24‐month post‐operative Banff Patellofemoral Instability Instrument (BPII) scores were assessed for differences in clinical outcomes between patients with and without patella alta. Pearson (for continuous variables) and Spearman rank correlations (for binary/ordinal variables) were calculated to determine the relationship between the patellar height ratio, demographic and pathoanatomic risk factors, and pre‐ and post‐operative BPII scores. ResultsPre‐ and post‐operative true‐lateral radiographs were admissible for 229/283 patients (81%) following isolated MPFL reconstruction. A statistically significant difference in the Caton‐Deschamps index was evident from pre‐ to post‐operative for the entire cohort (p < 0.001). The mean decrease in ratio was 0.03, and the effect size was 0.27, classified as small. Pre‐operatively 52/229 patients (22.7%) demonstrated a Caton‐Deschamps index ≥ 1.2, mean = 1.27 (SD = 0.08); post‐operatively 21/229 patients (9.2%) demonstrated patella alta, mean = 1.18, (SD = 0.10), p < 0.001 (two‐tailed). The mean decrease in the Caton‐Deschamps index for patients with pre‐operative patella alta was 0.10; the effect size was 0.82, classified as large. Pearson r correlation of patella alta to the pre‐ and post‐operative BPII scores demonstrated no statistically significant relationship. ConclusionThis study has demonstrated that treatment of lateral patellofemoral instability with an isolated MPFL reconstruction results in a statistically significant decrease in patellar height ratio, with the effect size being greatest in patients with higher pre‐operative Caton‐Deschamps indices. In patients that presented with patella alta, normalization of the patellar height ratio occurred in 31/52 (59.6%) of the cases. Pre‐operative patella alta was not associated with a statistically significant difference in disease‐specific BPII outcome scores at any time point. Given these findings, the utility and results of tibial tubercle distalization in patients with patella alta should be a focus of further research.Level of evidenceIV.

Normalisation of Patella Alta with MPFL Reconstruction Reduces the Prevalence of Risk Factors Associated With Recurrent Patella Dislocations - A Prospective Cross Sectional Study

“…Another 4 patients had instability symptoms without re-dislocation; of which three patients had 3 risk factors and one patient had 1 risk factor present respectively. Our re-dislocations rates were comparable to recent studies by Himestra et al (3.1%) [25] and Sappey-Marinier et al (4.7%) [29]. A meta-analysis found a 1.2% pooled total risk of recurrent instability after surgery [20].…”

“…There was a statistically signi cant reduction in the patella height of patients after MPFL reconstruction; CD ratio 1.18 ± 0.18 pre-operatively to 1.02 ± 0.16 post-operatively (p<0.001), IS ratio 1.16 ± 0.17 pre-operatively to 1.09 ± 0.16 post-operatively (p<0.001). This study, along with previous studies have shown that anatomical reconstruction of the MPFL consistently results in both a restraint to lateral translation, and decrease in patellar height [22][23][24][25][26].…”

“…Subsequently, Woodmass et al reported a reduction in patella alta from 34.0% pre-operatively to 12.5% post-operatively in an adult population [24]. Similarly, Himestra et al and Luceri et al found reduction in patella alta from 32.1% to 9.2% [25] and 35.8% to 7.4% [26] respectively after MPFL reconstruction. Approximately one third of patients 10 (30.3%) in our study had pre-operatively patella alta, with an eventual statistically signi cant 90% resultant normalisation of patella height to 1 patient (3%) (p<0.004).…”

“…It is believed that in addition to the restoration of the medial dynamic stabilisers, MPFL reconstruction reduces patella height due to the additional inferior vector angle. Several studies have reported that isolated MPFL reconstruction reduces the patella height measurements in patients with pre-operative patella alta [22][23][24][25][26].…”

Clinical Outcomes and Prognostic Factors in Patients With Recurrent Patellar Lateral Dislocation Treated With Isolated Medial Patellofemoral Ligament Reconstruction: A Retrospective Single-Center Analysis

“…A recent study conducted by Hiemstra et al 14 concluded that isolated MPFLR was able to correct mild patella alta in patients with patellar instability. 13 The outcomes again demonstrated the possible beneficial effect of MPFLR on other concomitant risk factors.…”