Identifying and modifying the impinging hip

Short summary of the thesis “Identifying and Modifying the Impinging Hip”
Femoroacetabular impingement syndrome (FAI-syndrome) is a well-known cause of groin complaints and young and active patients. This thesis covers the recognition of the FAI-syndrome, the available diagnostic modalities, and the treatment of the impinging hip by arthroscopic surgery. We describe how the FAI-syndrome can be recognized and what the incidence is in a general practitioner’s population. It is essential to identify the impinging structures in the hip joint, after FAI-syndrome recognition. For this aid, CT-scans are used, and 3D dynamic models are created to recognize the impinging areas of the hip joint. Treatment of FAI-syndrome is possible via surgical resection of the impinging morphologies, the modification of the hip. Results of this treatment can be measured using specifically designed questionnaires; the PROM; patient reported outcome measures.
This thesis contains eight published research articles.
One article describes the incidence of hip impingement in a large population of general practitioners, registered during a one-year period. The population was almost 110,000 patients large. We concluded that every general practitioner could identify at least three patients with FAI-syndrome yearly, but that the knowledge to recognize FAI-syndrome among general practitioners is limited.
The following article describes a validating study of a software to create 3D dynamic models out of CT scans of the hip joint. The software creates a moving hip joint and analyses whether impingement of the joint occurs that limits the normal range of motion. This study was conducted in cadaveric specimen in the Erasmus MC and validates the software for this purpose. The software was created by startup company from the TU Delft.
The following chapter of this thesis described the differences in sensitivity and specificity of the 3D software in comparison to regular radiographs in identification of hip impingement. These techniques were used in our large prospective cohort registration study. No significant differences could be identified in accuracy between the 3D software and regular radiographs in identification of impinging hip joints.
In chapter 5 we developed a traction force measurement device in cooperation with the TU Delft. This was added to the set-up for arthroscopic hip surgery, to measure the traction force needed to dislocate the hip joint during arthroscopy. These forces are high and can cause traction related neuropraxia (nerve damage) to the foot or perineum. We analyzed theses traction forces that were obliged to dislocate the hip joint to perform surgery (widening the joint space). We describe what we did to lower the traction forces and whether a correlation could be identified between the traction force and possible complications like neuropraxia. We could conclude that the traction force is high to dislocate the joint, that the traction force lowers during the arthroscopy after vacuum release, and after capsulotomy. No correlation could be identified between the traction force and the joint space widening. No clear correlation could be identified in amount of traction force and occurrence of nerve damage.
To measure the outcome and results of surgery specifically designed questionnaires are used that discuss pain and complaints. A specifically designed questionnaire for hip arthroscopy analyses is the HOS (Hip Outcome Score). We translated this questionnaire into Dutch and validated this questionnaire with our prospective registered data cohort. We conclude that the Dutch questionnaire is a reliable questionnaire to measure functional outcome after hip arthroscopy in patients with FAI-syndrome.
The functional outcome after hip arthroscopy for FAI-syndrome is analyzed in the next chapter. Short-term functional outcome results in a large patient cohort were described in this study. We can conclude that hip arthroscopy for FAI-syndrome results in a large and significant improvement in pain and function, one-year after surgery.
No all patients recover in equal amount after surgery. We created a risk-factor prediction model to better predict functional outcome after surgery in chapter 8. This model is based on specific pre-operative parameters to predicts whether patients successfully recover after hip arthroscopy for FAI-syndrome. This model can be used in the pre-operative counseling of patients to determine whether surgery is helpful or not.
In the final chapter, we describe two different recovery patterns in a large cohort of patients. In 100 prospectively registered patients, we analyze the differences in postoperative functional recovery after hip arthroscopy for FAI-syndrome and we identified two specific risk factors for group membership. The “improvers” after surgery and the “non-improvers” after surgery were identified. Risk factors to join the “non-improvers” were high pain scores pre-operatively and arthrosis of the femoral head.
This thesis covers the different aspects of identification of the FAI-syndrome, the diagnostic modalities and the treatment technique with the functional outcome results of hip arthroscopy for the impinging hip: identifying and modifying the impinging hip.