Multicentric, prospective observational data show sperm capacitation predicts male fertility, and cohort comparison reveals a high prevalence of impaired capacitation in men questioning their fertility

RESEARCH QUESTIONS

Can a previously defined relationship between sperm capacitation and the probability of a man generating pregnancy within three cycles, prospectively predict male fertility in diverse clinical settings? A second study asked, what is the prevalence of impaired sperm fertilizing ability in men questioning their fertility (MQF), and does this relate to traditional semen analysis metrics?

DESIGN

In the multicentric, prospective observational study, data (n = 128; six clinics) were analysed to test a published relationship between the percentage of fertilization-competent, capacitated spermatozoa (Cap-Score) and probability of generating pregnancy (PGP) within three cycles of intrauterine insemination. Logistic regression of total pregnancy outcomes (n = 252) assessed fit. In the cohort comparison, Cap-Scores of MQF (n = 2155; 22 clinics) were compared with those of 76 fertile men.

RESULTS

New outcomes (n = 128) were rank-ordered by Cap-Score and divided into quintiles (25-26 per group); chi-squared testing revealed no difference between predicted and observed pregnancies (P = 0.809). Total outcomes (n = 252; 128 new + 124 previous) were pooled and the model recalculated, yielding an improved fit (P < 0.001). Applying the Akaike information criterion found that the optimal model used Cap-Score alone. Cap-Scores were performed on 2155 men (with semen analysis data available for 1948). To compare fertilizing ability, men were binned by PGP (≤19%, 20-29%, 30-39%, 40-49%, 50-59%, ≥60%). Distributions of PGP and the corresponding Cap-Scores were significantly lower in MQF versus fertile men (P < 0.001). Notably, 64% of MQF with normal volume, concentration and motility (757/1183) had PGP of 39% or less (Cap-Scores ≤31), versus 25% of fertile men.

CONCLUSIONS

Sperm capacitation prospectively predicted male fertility. Impaired capacitation affects many MQF with normal semen analysis results, informing diagnosis versus idiopathic infertility.

The biomechanical efficacy of an oscillating K-wire driver

A new oscillating drill, designed for insertional ease and safety, was biomechanically tested using an MTS 812 servohydraulic material testing machine (Instrom). Holding strength and drilling force were compared against a traditional rotary drill using rabbit tibias to approximate the diameter and cortical thickness of human metacarpals. Three differently sized (0.028-, 0.045-, and 0.062-in. diameter) K-wires were evaluated for each drill. Mean peak axial load (drilling force) was significantly different for each wire driver type in each of the three sized K-wires (p < or = 0.01). The oscillating drill used an average of 3 N less force to penetrate either cortex. Mean peak pull-out force (holding strength) was higher for the oscillating drill, but the difference was not significant (p > or = 0.5). This study indicated that the oscillating drill required less force for insertion and had a similar holding strength as the rotary drill. In addition, our drill has been shown to be less damaging to surrounding soft tissues. This new type of drill is likely to be advantageous in the fields of hand, microsurgery, orthopedic, and plastic surgery, where bone fixation is often near vital neurovascular structures.