Revisiting the Holmlund and Hellsing Line: An Evaluation of the Anatomical Landmarks for Temporomandibular Joint Arthroscopy.

BACKGROUND: Historical surface landmarks along the Holmlund-Hellsing (H-H) line (10/-2 and 20/-10) are commonly used for temporomandibular joint (TMJ) arthroscopy, but prior studies suggest these points may be inaccurate. PURPOSE: Identify differences in puncture site locations between the H-H landmarks and an anatomical-based technique (ABT) for TMJ arthroscopy. STUDY DESIGN, SETTING, SAMPLE: The researchers implemented a prospective cohort study. Subjects included were patients who underwent level II TMJ arthroscopy for intra-articular pain and dysfunction from April 2019 to June 2021 at the Thomas Jefferson University Hospital. Inclusion criteria consisted of patients with a minimum follow-up of 1 month. Exclusion criteria included follow up less than 1 month, prior TMJ surgery, and benign or malignant joint pathology. PREDICTOR VARIABLE: Portal localization strategy: all procedures used ABT; H-H coordinates served as historical reference points for comparison. PRIMARY OUTCOME VARIABLE: Primary outcome was the distance between the postoperative arthroscopic puncture sites derived from the ABT versus the predicted punctures sites determined based on the H-H line. COVARIATES: The covariates included demographics (age and sex) and perioperative variables (laterality, diagnostic category, and Wilkes stage). ANALYSES: Nonparametric tests (Wilcoxon signed-rank test) were used to compare observed portal locations with historical Holmlund-Hellsing landmarks. Subgroup differences were assessed using the Wilcoxon rank-sum test for sex and laterality, and the Kruskal-Wallis test for age group, disease type, and Wilkes classification. Statistical significance was defined as P < .05. RESULTS: The study sample included 50 subjects, with a mean age of 36.7 ± 17.2 years (46, 92% female). For the fossa (posterior) portal, mean horizontal difference from the Holmlund-Hellsing landmark was 0.7 ± 1.5 mm anterior. Mean vertical difference was 2.1 ± 3.9 mm superior. Both differences were statistically significant from the historical landmark (horizontal, P = .0004; vertical, P < .0001). For the anterior recess portal, mean horizontal difference was 10.2 ± 4.7 mm anterior. The mean vertical difference was -7.4 ± 4.9 mm inferior. Both are statistically significantly different from the historical landmark (P < .001). CONCLUSIONS AND RELEVANCE: The traditional 20/-10 landmark approximates the fossa portal but does not accurately represent anterior recess portal location achieved using ABT.