Clinical predictors of outcome following hip arthroscopy

Abstract

Intra-articular hip pathology, including femoro-acetabular impingement syndrome (FAIS), is a cause of hip and groin pain in otherwise healthy young adults. While arthroscopic surgery in the hip joint has historically lagged behind its counterparts in the shoulder and knee, there has recently been a rapid evolution of the management of hip injuries in the young, active population utilizing hip arthroscopic techniques which has improved understanding of mechanical hip pathology. The aims of this thesis were to; investigate the clinical presentation of individuals scheduled to undergo hip arthroscopy; assess and report pre-operative deficits in hip strength, range of movement (ROM) and dynamic balance; determine the changes that occur post surgery, and; identify potentially modifiable predictors of outcome post arthroscopy.A review of literature revealed that there is limited evidence that those with FAI syndrome have reduced hip abduction and flexion ROM compared to healthy matched controls. There were no differences in hip adduction or extension ROM, and conflicting results for external rotation and internal rotation ROM. However, people with symptomatic FAIS demonstrated deficits in hip muscle strength and reduced dynamic balance on one leg when compared to controls. For hip joint ROM, there were no significant within-group differences between pre and post intervention time points while hip muscle strength improved significantly from pre to post-hip arthroscopy in a single case series.In people undergoing hip arthroscopy, severe femoral head chondropathy, large labral tears, along with a high prevalence of labral pathology and acetabular chondropathy, were relatively common findings. Severe femoral head chondropathy and large labral tears were most associated with patient related outcomes (PROs), however, at best only explained 22% of the variability. Individuals with hip pain and severe scores in the International Hip Outcome Tool (iHOT33) subscale of symptoms and functional limitations presented with significantly lesser hip muscle strength and hip flexion ROM when compared to individuals with moderate or mild scores. Individuals scheduled for arthroscopic hip surgery were also significantly weaker, had less hip mobility and reduced dynamic balance compared to healthy matched controls. In the hip pain population, dynamic balance performance was associated with various hip strength and ROM measurements in a direction specific manner. The clinical significance of these findings may assist therapists in providing targeted rehabilitation programs for people with FAIS and chondrolabral hip pain to improve hip strength and ROM, help reduce symptoms and to improve function.By three months post arthroscopy to address bony morphology and/or chondrolabral pathology, all directions of hip strength (with the exception of adduction squeeze in crook lying and flexion) and hip flexion ROM were significantly improved. While by six months post arthroscopy, strength in all directions, and flexion and rotation ROM were significantly improved in both limbs, hip flexion, internal rotation (IR), external rotation (ER) strength, and IR ROM remained significantly lower than healthy matched controls in both limbs. As a consequence of these findings, it may be concluded that progression of activity during post arthroscopy rehabilitation should be based on the measured recovery of hip strength and ROM, and caution should be displayed regarding return to sport prior to six months. These findings are of high clinical relevance for the surgeons and physiotherapists who provide rehabilitation guidance to individuals after hip arthroscopy.Predictors of self-reported improvement at six months post hip arthroscopy include hip flexion strength and bodyweight. At six months post arthroscopy, sixty-seven percent of individuals in this study reported a minimal important change (MIC) of more than ten points on the iHOT33. While iHOT33 scores were significantly improved post arthroscopy, the average score of 60/100 does not reflect optimal hip function. Eighty-five percent of those with hip flexion strength of less than 287.5 Newtons (N) and who weighed less than 89.5 kilograms (kg) reported an iHOT33 MIC post-surgery, compared to only 40% of those who weighed more than 89.5kg. Only 20% of individuals with hip flexion strength greater than 287.5N reported MIC and the odds of improving were fifteen times lower than those who were weaker than 287.5N and lighter than 89.5kg. People with weaker hip flexors pre-operatively may have adopted reactive muscle activation strategies to reduce load on the anterior aspect of the labrum. Reduced strength may also be a surrogate for greater pain with loaded activity. Those with greater pain and lesser strength may have greater potential for improvement in hip function following surgery and subsequent rehabilitation than those who are already strong. The identification of modifiable predictors may be combined with other established predictors to help shape surgical and non-surgical decision-making and forecast potential outcomes following surgical intervention.